MAIN

This Quarterly Report on Form 10-Q contains forward-looking statements regarding the plans and objectives of management for future operations and which relate to future events or our future performance or financial condition. Any such forward-looking statements may involve known and unknown risks, uncertainties and other factors which may cause our actual results, performance or achievements to be materially different from future results, performance or achievements expressed or implied by any forward-looking statements. Forward-looking statements, which involve assumptions and describe our future plans, strategies and expectations, are generally identifiable by use of the words “may,” “will,” “should,” “expect,” “anticipate,” “estimate,” “believe,” “intend” or “project” or the negative of these words or other variations on these words or comparable terminology. These forward-looking statements are based on assumptions that may be incorrect, and we cannot assure you that the projections included in these forward-looking statements will come to pass. Our actual results could differ materially from those expressed or implied by the forward-looking statements as a result of various factors, including, without limitation, the factors referenced in Item 1A entitled “Risk Factors” below in this Quarterly Report on Form 10-Q, if any, and discussed in Item 1A entitled “Risk Factors” in our Annual Report on Form 10-K for the year ended December 31, 2025, filed with the Securities and Exchange Commission (“SEC”) on February 27, 2026 and elsewhere in this Quarterly Report on Form 10-Q and our other SEC filings. Other factors that could cause actual results to differ materially include changes in the economy and future changes in laws or regulations and conditions in our operating areas. We have based the forward-looking statements included in this Quarterly Report on Form 10-Q on information available to us on the date of this Quarterly Report on Form 10-Q, and we assume no obligation to update any such forward-looking statements, unless we are required to do so by applicable law. However, you are advised to refer to any additional disclosures that we may make directly to you or through reports that we in the future may file with the SEC, including subsequent periodic and current reports. This discussion should be read in conjunction with our consolidated financial statements as of December 31, 2025, and for the year then ended, and Management’s Discussion and Analysis of Financial Condition and Results of Operations, both contained in our Annual Report on Form 10-K for the year ended December 31, 2025, as well as the consolidated financial statements (unaudited) and notes to the consolidated financial statements (unaudited) contained in this report. ORGANIZATION Main Street Capital Corporation (“MSCC” or, together with its consolidated subsidiaries, “Main Street” or the “Company”) is a principal investment firm primarily focused on providing customized long-term debt and equity capital solutions to lower middle market (“LMM”) companies (its “LMM investment strategy”) and debt capital to private (“Private Loan”) companies owned by or in the process of being acquired by a private equity fund (its “Private Loan investment strategy”). Main Street’s portfolio investments are typically made to support management buyouts, recapitalizations, growth financings, refinancings and acquisitions of companies that operate in diverse industry sectors. Main Street seeks to partner with entrepreneurs, business owners and management teams and generally provides “one-stop” debt and equity financing solutions within its LMM investment strategy. Main Street invests primarily in secured debt investments, equity investments, warrants and other securities of LMM companies typically based in the U.S. Main Street also seeks to partner with private equity fund sponsors in its Private Loan investment strategy and primarily invests in secured debt investments of Private Loan companies generally headquartered in the U.S. Main Street also maintains a legacy portfolio of investments in larger middle market (“Middle Market”) companies (its “Middle Market investment portfolio”) and a limited portfolio of other portfolio (“Other Portfolio”) investments. Main Street’s Middle Market investments are generally debt investments in companies owned by a private equity fund that were originally issued through a syndication financing process. Main Street has generally stopped making new Middle Market investments and expects the size of its Middle Market investment portfolio to continue to decline in future periods as its existing Middle Market investments are repaid or sold. Main Street’s Other Portfolio investments primarily consist of investments that are not consistent with the typical profiles for its LMM, Private Loan or Middle Market portfolio investments, including investments in unaffiliated investment companies and private funds managed by third parties. The “Investment Portfolio,” as used herein, refers to all of Main Street’s investments in LMM portfolio companies, investments in Private Loan portfolio companies, investments in Middle Market portfolio companies, Other Portfolio investments, short-term portfolio investments (see Note C — Fair Value Hierarchy for Investments — Portfolio Composition — Investment Portfolio Composition in the notes to the consolidated financial statements included in Item 1. Consolidated Financial Statements of this Quarterly Report on Form 10-Q) and the investment in the External Investment Manager (as defined below). 133 Table of contents MSCC was formed in March 2007 to operate as an internally managed business development company (“BDC”) under the Investment Company Act of 1940, as amended (the “1940 Act”). Because MSCC is internally managed, all of the executive officers and other employees are employed by MSCC. Therefore, MSCC does not pay any external investment advisory fees, but instead directly incurs the operating costs associated with employing investment and portfolio management professionals. MSCC wholly owns several investment funds, including Main Street Mezzanine Fund, LP (“MSMF”) and Main Street Capital III, LP (“MSC III” and, together with MSMF, the “Funds”), and each of their general partners. The Funds are each licensed as a Small Business Investment Company (“SBIC”) by the U.S. Small Business Administration (“SBA”). MSC Adviser I, LLC (the “External Investment Manager”) was formed in November 2013 as a wholly-owned subsidiary of Main Street to provide investment management and other services to parties other than Main Street (“External Parties”) and earns fee income for such services. MSCC has been granted no-action relief by the SEC to allow the External Investment Manager to register as a registered investment adviser under the Investment Advisers Act of 1940, as amended. Since the External Investment Manager conducts all of its investment management activities for External Parties, it is accounted for as a portfolio investment of Main Street and is not included as a consolidated subsidiary in Main Street’s consolidated financial statements. MSCC has elected to be treated for U.S. federal income tax purposes as a regulated investment company (“RIC”) under Subchapter M of the Internal Revenue Code of 1986, as amended (the “Code”). As a result, MSCC generally does not pay corporate-level U.S. federal income taxes on any net ordinary taxable income or capital gains that it distributes to its stockholders. MSCC has certain direct and indirect wholly-owned subsidiaries that have elected to be taxable entities (the “Taxable Subsidiaries”). The primary purpose of the Taxable Subsidiaries is to permit MSCC to hold equity investments in portfolio companies which are “pass-through” entities for tax purposes. MSCC also has certain direct and indirect wholly-owned subsidiaries formed for financing purposes (the “Structured Subsidiaries”). Unless otherwise noted or the context otherwise indicates, the terms “we,” “us,” “our,” the “Company” and “Main Street” refer to MSCC and its consolidated subsidiaries, which include the Funds, the Taxable Subsidiaries and the Structured Subsidiaries. OVERVIEW OF OUR BUSINESS Our principal investment objective is to maximize our Investment Portfolio’s total return by generating current income from our debt investments and current income and capital appreciation from our equity and equity-related investments, including warrants, convertible securities and other rights to acquire equity securities in a portfolio company. We seek to achieve our investment objective primarily through our LMM and Private Loan investment strategies. Our LMM investment strategy involves investments in companies that generally have annual revenues between $10 million and $150 million and annual earnings before interest, tax, depreciation and amortization expenses (“EBITDA”) between $3 million and $20 million. Our LMM portfolio investments generally range in size from $5 million to $125 million. Our Private Loan investment strategy involves investments in companies that generally have annual revenues between $25 million and $500 million and annual EBITDA between $7.5 million and $50 million. Our Private Loan investments generally range in size from $10 million to $100 million. We seek to fill the financing gap for LMM businesses, which, historically, have had limited access to financing from commercial banks and other traditional sources. The underserved nature of the LMM creates the opportunity for us to meet the financing needs of LMM companies while also negotiating favorable transaction terms and equity participation. Our ability to invest across a company’s capital structure, from secured loans to equity securities, allows us to offer portfolio companies a comprehensive suite of financing options, or a “one-stop” financing solution. We believe that providing customized, “one-stop” financing solutions is important and valuable to LMM portfolio companies. We generally seek to partner directly with entrepreneurs, management teams and business owners in making our LMM investments. Our LMM portfolio debt investments are generally secured by a first priority lien on the assets of the portfolio company and typically have a term of between five and seven years from the original investment date. Private Loan investments primarily consist of debt securities that have primarily been originated directly by us or, to a lesser extent, through our strategic relationships with other investment funds on a collaborative basis through investments that are often referred to in the debt markets as “club deals” because of the small lender group size. In both cases, our Private Loan investments are typically made in a company owned by or in the process of being acquired by a private equity fund. Our Private Loan portfolio debt investments are generally secured by a first priority lien on the assets of the portfolio company and typically have a term of between three and seven years from the original investment date. We may also co-invest with the private equity fund in the equity securities of our Private Loan portfolio companies. 134 Table of contents We also maintain a legacy portfolio of investments in larger Middle Market companies. Our Middle Market investments are generally debt investments in companies owned by a private equity fund that were originally issued through a syndication financing process. We have generally stopped making new Middle Market investments and expect the size of our Middle Market investment portfolio to continue to decline in future periods as existing Middle Market investments are repaid or sold. Our Middle Market debt investments generally range in size from $3 million to $25 million, are generally secured by a first priority lien on the assets of the portfolio company and typically have an expected duration of between three and seven years from the original investment date. Our Other Portfolio investments primarily consist of investments that are not consistent with the typical profiles for our LMM, Private Loan or Middle Market portfolio investments, including investments in unaffiliated investment companies and private funds which may be managed by third parties. In our Other Portfolio, we may incur indirect fees and expenses in connection with investments managed by third parties, such as investments in other investment companies or private funds. Based upon our liquidity and capital structure management activities, our Investment Portfolio may also periodically include short-term portfolio investments that are atypical of our LMM and Private Loan portfolio investments in that they are intended to be a short-term deployment of capital. These assets are typically expected to be realized in one year or less and are not expected to be a significant portion of our overall Investment Portfolio. Our external asset management business is conducted through the External Investment Manager. The External Investment Manager earns management fees based on the assets of the funds under management and may earn incentive fees, or a carried interest, based on the performance of the funds managed. Our portfolio investments are generally made through MSCC, the Taxable Subsidiaries, the Funds and the Structured Subsidiaries. MSCC, the Taxable Subsidiaries, the Funds and the Structured Subsidiaries share the same investment strategies and criteria, although they are subject to different regulatory regimes. An investor’s return in MSCC will depend, in part, on the Taxable Subsidiaries’, the Funds’ and the Structured Subsidiaries’ investment returns as they are wholly-owned subsidiaries of MSCC. The level of new portfolio investment activity will fluctuate from period to period based upon our view of the current economic fundamentals, our ability to identify new investment opportunities that meet our investment criteria and our ability to consummate the identified opportunities. The level of new investment activity, and associated interest and fee income, will directly impact future investment income. In addition, the level of dividends paid by portfolio companies and the portion of our portfolio debt investments on non-accrual status will directly impact future investment income. While we intend to grow our portfolio and our investment income over the long term, our growth and our operating results may be more limited during depressed economic periods. However, we intend to appropriately manage our cost structure and liquidity position based on applicable economic conditions and our investment outlook. The level of realized gains or losses and unrealized appreciation or depreciation on our investments will also fluctuate depending upon portfolio activity, economic conditions and the performance of our individual portfolio companies. The changes in realized gains and losses and unrealized appreciation or depreciation could have a material impact on our operating results. Because we are internally managed, we do not pay any external investment advisory fees, but instead directly incur the operating costs associated with employing investment and portfolio management professionals. We believe that our internally managed structure provides us with a better alignment of interests between our management team and our employees and our stockholders and a beneficial operating expense structure when compared to other publicly traded and privately held investment firms which are externally managed, and our internally managed structure allows us the opportunity to leverage our non-interest operating expenses as we grow our Investment Portfolio and our External Investment Manager’s asset management business (as described below). The ratio of our total operating expenses, excluding interest expense, as a percentage of our quarterly average total assets was 1.3% for each of the trailing twelve months ended June 30, 2026 and 2025 and for the year ended December 31, 2025. The ratio of our total operating expenses, including interest expense, as a percentage of our quarterly average total assets was 3.7% and 3.8% for the trailing twelve months ended June 30, 2026 and 2025, respectively, and 3.7% for the year ended December 31, 2025. Our ratio of expenses as a percentage of our average net asset value (“NAV”) is described in greater detail in Note F — Financial Highlights in the notes to the consolidated financial statements included in Item 1. Consolidated Financial Statements of this Quarterly Report on Form 10-Q. 135 Table of contents The External Investment Manager serves as the investment adviser and administrator to MSC Income Fund, Inc. (“MSC Income”) pursuant to an Investment Advisory and Administrative Services Agreement entered into in October 2020 between the External Investment Manager and MSC Income (as amended and restated on January 29, 2025, the “Advisory Agreement”). Under the Advisory Agreement, prior to January 29, 2025, the External Investment Manager earned a 1.75% annual base management fee on MSC Income’s average total assets, a subordinated incentive fee on income equal to 20% of pre-incentive fee net investment income above a specified investment return hurdle rate and a 20% incentive fee on cumulative net realized capital gains in exchange for providing advisory services to MSC Income. On and after January 29, 2025, under the Advisory Agreement, the External Investment Manager earns a 1.5% annual base management fee on MSC Income’s average total assets (including cash and cash equivalents), payable quarterly in arrears (with additional future contractual reductions based upon changes to MSC Income’s investment portfolio composition), a subordinated incentive fee on income equal to 17.5% of pre-incentive fee net investment income above a specified investment return hurdle rate, subject to a 50% / 50% catch-up feature, and a 17.5% incentive fee on cumulative net realized capital gains from January 29, 2025. Additionally, the External Investment Manager has entered into investment management agreements with MS Private Loan Fund I, LP (“Private Loan Fund I”) and MS Private Loan Fund II, LP (“Private Loan Fund II”), each a private investment fund with a strategy to co-invest with Main Street in Private Loan portfolio investments, pursuant to which the External Investment Manager provides investment advisory and management services to each fund in exchange for an asset-based management fee and certain incentive fees. The External Investment Manager may also advise other clients, including funds and separately managed accounts, pursuant to advisory and services agreements with such clients in exchange for asset-based and incentive fees. The External Investment Manager earns management fees based on the assets of the funds and accounts under management and may earn incentive fees, or a carried interest, based on the performance of the funds and accounts managed. For the three months ended June 30, 2026 and 2025, the External Investment Manager earned $6.2 million and $5.7 million in base management fees, respectively, $3.0 million and $3.7 million in incentive fees, net of waivers, respectively, and $0.2 million of administrative service fee income for each of the three months ended June 30, 2026 and 2025. For the six months ended June 30, 2026 and 2025, the External Investment Manager earned $12.3 million and $11.5 million in base management fees, respectively, $6.0 million and $6.4 million in incentive fees, net of waivers, respectively, and $0.4 million and $0.3 million of administrative service fee income, respectively. For the three and six months ended June 30, 2026, the External Investment Manager waived $0.3 million and $1.2 million, respectively, of incentive fees on income related to MSC Income. As of June 30, 2026, MSC Income had an expense accrual of $5.1 million of incentive fees on capital gains to the External Investment Manager. However, no capital gains incentive fees were currently contractually payable to the External Investment Manager as of June 30, 2026 and as a result no amounts were accrued by the External Investment Manager. We have entered into an agreement with the External Investment Manager to share employees in connection with its asset management business generally, and specifically for its relationship with MSC Income and its other clients. Through this agreement, we share employees with the External Investment Manager, including their related infrastructure, business relationships, management expertise and capital raising capabilities, and we allocate the related expenses to the External Investment Manager pursuant to the sharing agreement. Our total expenses for the three months ended June 30, 2026 and 2025 are net of expenses allocated to the External Investment Manager of $6.6 million and $5.9 million, respectively. Our total expenses for the six months ended June 30, 2026 and 2025 are net of expenses allocated to the External Investment Manager of $12.1 million and $11.2 million, respectively The total contribution of the External Investment Manager to our net investment income consists of the combination of the expenses allocated to the External Investment Manager and the dividend income earned from the External Investment Manager. For the three months ended June 30, 2026 and 2025, dividends earned by us from the External Investment Manager were $2.1 million and $2.8 million, respectively. For each of the three months ended June 30, 2026 and 2025, the total contribution of the External Investment Manager to our net investment income was $8.7 million. For the six months ended June 30, 2026 and 2025, dividends earned by us from the External Investment Manager were $5.0 million and $5.3 million, respectively. For the six months ended June 30, 2026 and 2025, the total contribution of the External Investment Manager to our net investment income was $17.0 million and $16.6 million, respectively. 136 Table of contents We have received an exemptive order from the SEC permitting co-investments among us, MSC Income and other advisory clients of the External Investment Manager in certain negotiated transactions where co-investing would otherwise be prohibited under the 1940 Act. We have made co-investments with, and in the future intend to continue to make co-investments with MSC Income, Private Loan Fund I, Private Loan Fund II and other advisory clients of the External Investment Manager, in accordance with the conditions of the order. Because the External Investment Manager may earn performance-based fee compensation from its advisory clients, this may provide the Company and the External Investment Manager an incentive to allocate opportunities to advisory clients instead of us. However, both we and the External Investment Manager have adopted policies and procedures pursuant to the order to manage this conflict and ensure that investment opportunities are allocated in a manner that is fair and equitable considering each investor’s interests, including oversight of the co-investment program by the independent members of our and MSC Income’s boards of directors and their required approval of certain co-investment transactions thereunder. In addition to the co-investment program described above, we also co-invest in certain investment transactions where price is the only negotiated point by us and our affiliates. INVESTMENT PORTFOLIO SUMMARY A summary of our LMM and Private Loan portfolio investments as of June 30, 2026 and December 31, 2025 is as follows (this information excludes Middle Market portfolio investments, Other Portfolio investments and the External Investment Manager, which are discussed further below): June 30, 2026 LMM (a) Private Loan (dollars in millions) Number of portfolio companies 94 86 Fair value $ 3,205.6 $ 2,090.9 Cost $ 2,547.7 $ 2,123.5 Debt investments as a % of portfolio (at cost) 71.1 % 94.3 % Equity investments as a % of portfolio (at cost) 28.9 % 5.7 % % of debt investments at cost secured by first priority lien 99.4 % 99.3 % Weighted-average annual effective yield (b) 12.6 % 10.2 % Average EBITDA (c) $ 11.8 $ 39.3 ___________________________ (a)As of June 30, 2026, we had equity ownership in all of our LMM portfolio companies, and the average fully diluted equity ownership in those portfolio companies was 36%. (b)The weighted-average annual effective yields were computed using the effective interest rates for all debt investments as of June 30, 2026, including amortization of deferred debt origination fees and accretion of original issue discount but excluding fees payable upon repayment of the debt investments and any debt investments on non-accrual status, and are weighted based upon the principal amount of each applicable debt investment as of June 30, 2026. The weighted-average annual effective yield on our debt portfolio as of June 30, 2026, including debt investments on non-accrual status, was 12.1% for our LMM portfolio investments and 9.6% for our Private Loan portfolio investments. The weighted-average annual effective yield is not reflective of what an investor in shares of our common stock will realize on their investment because it does not reflect changes in the market value of our stock, our utilization of debt capital in our capital structure, our expenses or any sales load paid by an investor. (c)The average EBITDA is calculated using a simple average for the LMM portfolio companies and a weighted-average for the Private Loan portfolio companies. These calculations exclude certain portfolio companies, including six LMM portfolio companies and five Private Loan portfolio companies, as EBITDA is not a meaningful valuation metric for our investments in these portfolio companies, and those portfolio companies whose primary purpose is to own real estate and those portfolio companies whose primary operations have ceased and only residual value remains. 137 Table of contents December 31, 2025 LMM (a) Private Loan (dollars in millions) Number of portfolio companies 92 86 Fair value $ 3,057.0 $ 1,988.4 Cost $ 2,419.3 $ 2,014.1 Debt investments as a % of portfolio (at cost) 71.2 % 93.5 % Equity investments as a % of portfolio (at cost) 28.8 % 6.5 % % of debt investments at cost secured by first priority lien 99.4 % 99.9 % Weighted-average annual effective yield (b) 12.5 % 10.5 % Average EBITDA (c) $ 11.1 $ 33.9 ___________________________ (a)As of December 31, 2025, we had equity ownership in all of our LMM portfolio companies, and the average fully diluted equity ownership in those portfolio companies was 37%. (b)The weighted-average annual effective yields were computed using the effective interest rates for all debt investments as of December 31, 2025, including amortization of deferred debt origination fees and accretion of original issue discount but excluding fees payable upon repayment of the debt investments and any debt investments on non-accrual status, and are weighted based upon the principal amount of each applicable debt investment as of December 31, 2025. The weighted-average annual effective yield on our debt portfolio as of December 31, 2025, including debt investments on non-accrual status, was 12.0% for our LMM portfolio investments and 10.1% for our Private Loan portfolio investments. The weighted-average annual effective yield is not reflective of what an investor in shares of our common stock will realize on their investment because it does not reflect changes in the market value of our stock, our utilization of debt capital in our capital structure, our expenses or any sales load paid by an investor. (c)The average EBITDA is calculated using a simple average for the LMM portfolio companies and a weighted-average for the Private Loan portfolio companies. These calculations exclude certain portfolio companies, including five LMM portfolio companies and six Private Loan portfolio companies, as EBITDA is not a meaningful valuation metric for our investments in these portfolio companies, and those portfolio companies whose primary purpose is to own real estate and those portfolio companies whose primary operations have ceased and only residual value remains. As of June 30, 2026, we had Other Portfolio investments in 34 entities, spread across 13 investment managers, collectively totaling $141.3 million in fair value and $150.8 million in cost basis, which comprised 2.5% and 3.0% of our Investment Portfolio at fair value and cost, respectively. As of December 31, 2025, we had Other Portfolio investments in 33 entities, spread across 13 investment managers, collectively totaling $134.1 million in fair value and $141.6 million in cost basis, which comprised 2.4% and 3.0% of our Investment Portfolio at fair value and cost, respectively. As of June 30, 2026, we had Middle Market portfolio investments in 11 portfolio companies, collectively totaling $83.1 million in fair value and $123.1 million in cost basis, which comprised 1.4% and 2.5% of our Investment Portfolio at fair value and cost, respectively. As of December 31, 2025, we had Middle Market portfolio investments in 11 portfolio companies, collectively totaling $83.5 million in fair value and $120.1 million in cost basis, which comprised 1.5% and 2.5% of our Investment Portfolio at fair value and cost, respectively. As previously discussed in Note A.1. — Organization and Basis of Presentation — Organization in the notes to the consolidated financial statements included in Item 1. Consolidated Financial Statements of this Quarterly Report on Form 10-Q, we hold an investment in the External Investment Manager, a wholly-owned subsidiary that is treated as a portfolio investment. As of June 30, 2026, this investment had a fair value of $225.2 million and a cost basis of $29.5 million, which comprised 3.9% and 0.6% of our Investment Portfolio at fair value and cost, respectively. As of December 31, 2025, this investment had a fair value of $255.0 million and a cost basis of $29.5 million, which comprised 4.6% and 0.6% of our Investment Portfolio at fair value and cost, respectively. 138 Table of contents For the three months ended June 30, 2026 and 2025, we achieved an annualized total return on investments of 17.3% and 16.4%, respectively. For the six months ended June 30, 2026 and 2025, we achieved an annualized total return on investments of 13.2% and 16.2%, respectively. For the year ended December 31, 2025, we achieved a total return on investments of 16.4%. Total return on investments equals the total interest, dividend and fee income plus realized and unrealized changes in the fair value of the Investment Portfolio divided by the average quarterly Investment Portfolio balance at cost, in each case for the specified period. Our total return on investments is not reflective of what an investor in shares of our common stock will realize on their investment because it does not reflect changes in the market value of our stock, our utilization of debt capital in our capital structure, our expenses or any sales load paid by an investor. CRITICAL ACCOUNTING POLICIES The preparation of financial statements and related disclosures in conformity with generally accepted accounting principles in the United States of America (“U.S. GAAP”) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, and contingent assets and liabilities as of the date of the financial statements, and revenues and expenses during the periods reported. Actual results could materially differ from those estimates. Critical accounting policies are those that require management to make subjective or complex judgments about the effect of matters that are inherently uncertain and may change in subsequent periods. Changes that may be required in the underlying assumptions or estimates in these areas could have a material impact on our current and future financial condition and results of operations. Management has discussed the development and selection of each critical accounting policy and estimate with the Audit Committee of the Board of Directors. Our critical accounting policies and estimates include the Investment Portfolio Valuation and Revenue Recognition policies described below. Our significant accounting policies are described in greater detail in Note B — Summary of Significant Accounting Policies in the notes to the consolidated financial statements included in Item 1. Consolidated Financial Statements of this Quarterly Report on Form 10-Q. Investment Portfolio Valuation The most significant determination inherent in the preparation of our consolidated financial statements is the valuation of our Investment Portfolio and the related amounts of unrealized appreciation and depreciation. We consider this determination to be a critical accounting estimate, given the significant judgments and subjective measurements required. As of both June 30, 2026 and December 31, 2025, our Investment Portfolio valued at fair value represented 97% of our total assets. We are required to report our investments at fair value. We follow the provisions of Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) 820, Fair Value Measurements and Disclosures (“ASC 820”). ASC 820 defines fair value, establishes a framework for measuring fair value, establishes a fair value hierarchy based on the quality of inputs used to measure fair value and enhances disclosure requirements for fair value measurements. ASC 820 requires us to assume that the portfolio investment is to be sold in the principal market to independent market participants, which may be a hypothetical market. Market participants are defined as buyers and sellers in the principal market that are independent, knowledgeable and willing and able to transact. See Note B.1. — Summary of Significant Accounting Policies — Valuation of the Investment Portfolio in the notes to the consolidated financial statements included in Item 1. Consolidated Financial Statements of this Quarterly Report on Form 10-Q for a detailed discussion of our Valuation Procedures (as defined below). Due to the inherent uncertainty in the valuation process, our determination of fair value for our Investment Portfolio may differ materially from the values that would have been determined had a ready market for the securities existed. In addition, changes in the market environment, portfolio company performance and other events that may occur over the lives of the investments may cause the gains or losses ultimately realized on these investments to be materially different than the valuations currently assigned. We determine the fair value of each individual investment and record changes in fair value as unrealized appreciation or depreciation. Rule 2a-5 under the 1940 Act permits a BDC’s board of directors to designate its executive officers or investment adviser as a valuation designee to determine the fair value for its investment portfolio, subject to the active oversight of the board. Our Board of Directors has approved policies and procedures pursuant to Rule 2a-5 (the “Valuation Procedures”) and has designated a group of our executive officers to serve as the Board of Directors’ valuation designee. We believe our Investment Portfolio as of June 30, 2026 and December 31, 2025 approximates fair value as of those dates based on the markets in which we operate and other conditions in existence on those reporting dates. 139 Table of contents Revenue Recognition Interest and Dividend Income We record interest and dividend income on the accrual basis to the extent amounts are expected to be collected. Dividend income is recorded as dividends are declared by the portfolio company or at the point an obligation exists for the portfolio company to make a distribution. We evaluate accrued interest and dividend income periodically for collectability. When a loan or debt security becomes 90 days or more past due, and if we otherwise do not expect the debtor to be able to service its debt obligation, we will generally place the loan or debt security on non-accrual status and cease recognizing interest income on that loan or debt security until the borrower has demonstrated the ability and intent to pay contractual amounts due. If a loan or debt security’s status significantly improves regarding the debtor’s ability to service the debt obligation, or if a loan or debt security is repaid, sold or written off, we remove it from non-accrual status. Generally, any interest payments received from investments on non-accrual status reduce the cost basis of our investment and are not recorded as income. Fee Income We may periodically provide services, including structuring and advisory services, to our portfolio companies or other third parties. For services that are separately identifiable and evidence exists to substantiate fair value, fee income is recognized as earned, which is generally when the investment or other applicable transaction closes. Fees received in connection with debt financing transactions for services that do not meet these criteria are treated as debt origination fees and are generally deferred and accreted into income over the life of the financing. Payment-in-Kind (“PIK”) Interest and Cumulative Dividends We hold certain debt and preferred equity instruments in our Investment Portfolio that contain PIK interest and cumulative dividend provisions. The PIK interest, computed at the contractual rate specified in each debt agreement, is periodically added to the principal balance of the debt and is recorded as interest income. Thus, the actual collection of this interest may be deferred until the time of debt principal repayment. Cumulative dividends are recorded as dividend income, and any dividends in arrears are added to the balance of the preferred equity investment. The actual collection of these dividends in arrears may be deferred until such time as the preferred equity is redeemed or sold. To maintain RIC tax treatment (see Note B.10. — Summary of Significant Accounting Policies — Income Taxes in the notes to the consolidated financial statements included in Item 1. Consolidated Financial Statements of this Quarterly Report on Form 10-Q), these non-cash sources of income may need to be paid out to stockholders in the form of distributions, even though we may not have collected the PIK interest and cumulative dividends in cash. We stop accruing PIK interest and cumulative dividends and write off any accrued and uncollected interest and dividends in arrears when we determine that such PIK interest and dividends in arrears are no longer collectible. For the three months ended June 30, 2026 and 2025, (i) 2.9% and 2.3%, respectively, of our total investment income was attributable to PIK interest income not paid currently in cash and (ii) 0.7% and 0.9%, respectively, of our total investment income was attributable to cumulative dividend income not paid currently in cash. For the six months ended June 30, 2026 and 2025, 2.8% and 2.6%, respectively, of our total investment income was attributable to PIK interest income not paid currently in cash. For each of the six months ended June 30, 2026 and 2025, 0.7% of our total investment income was attributable to cumulative dividend income not paid currently in cash. 140 Table of contents INVESTMENT PORTFOLIO COMPOSITION A summary of the composition of our total combined LMM, Private Loan and Middle Market portfolio investments at cost and fair value by type of investment as a percentage of the total combined LMM, Private Loan and Middle Market portfolio investments as of June 30, 2026 and December 31, 2025 is as follows (this information excludes Other Portfolio investments and the External Investment Manager, which are discussed above): Cost: June 30, 2026 December 31, 2025 First lien debt 80.9 % 80.9 % Equity 18.3 18.6 Second lien debt 0.4 0.1 Equity warrants 0.2 0.2 Other 0.2 0.2 100.0 % 100.0 % Fair Value: June 30, 2026 December 31, 2025 First lien debt 69.6 % 69.8 % Equity 29.4 29.4 Second lien debt 0.3 — Equity warrants 0.5 0.6 Other 0.2 0.2 100.0 % 100.0 % Our LMM, Private Loan and Middle Market portfolio investments carry a number of risks including: (1) investing in companies which may have limited operating histories and financial resources; (2) holding investments that generally are not publicly traded and which may be subject to legal and other restrictions on resale; and (3) other risks common to investing in below investment-grade debt and equity investments in our Investment Portfolio. See Item 1A. Risk Factors contained in Part II of this Form 10-Q for further information. PORTFOLIO ASSET QUALITY We utilize an internally developed investment rating system to rate the performance of each LMM, Private Loan and Middle Market portfolio company and to monitor our expected level of returns on each of our LMM, Private Loan and Middle Market investments in relation to our expectations for the portfolio company. The investment rating system takes into consideration various factors, including, but not limited to, each investment’s expected level of returns, the collectability of our debt investments and the ability to receive a return of the invested capital in our equity investments, comparisons to competitors and other industry participants, the portfolio company’s future outlook and other factors that are deemed to be significant to the portfolio company. As of June 30, 2026, investments on non-accrual status were $65.2 million at fair value and $198.5 million at cost and comprised 1.1% and 4.0% of our total Investment Portfolio at fair value and cost, respectively. As of December 31, 2025, investments on non-accrual status were $56.3 million at fair value and $155.3 million at cost and comprised 1.0% and 3.3% of our total Investment Portfolio at fair value and cost, respectively. The operating results of our portfolio companies are impacted by changes in the broader fundamentals of the U.S. economy. In periods during which the U.S. economy contracts, it is likely that the financial results of small to mid-sized companies, like those in which we invest, could experience deterioration or limited growth from current levels, which could ultimately lead to difficulty in meeting their debt service requirements, to an increase in defaults on our debt investments or in realized losses on our investments and to difficulty in maintaining historical dividend payment rates and unrealized appreciation on our equity investments. Consequently, we can provide no assurance that the performance of certain portfolio companies will not be negatively impacted by future economic cycles or other conditions, which could also have a negative impact on our future results. 141 Table of contents DISCUSSION AND ANALYSIS OF RESULTS OF OPERATIONS Comparison of the three months ended June 30, 2026 and 2025 Set forth below is a comparison of the results of operations and a reconciliation of net investment income to distributable net investment income and to distributable net investment income before taxes for the three months ended June 30, 2026 and 2025. Three Months Ended June 30, Net Change 2026 2025 Amount % (dollars in thousands) Total investment income $ 149,572 $ 143,973 $ 5,599 4 % Total expenses (55,775) (50,639) (5,136) 10 % Net investment income before taxes 93,797 93,334 463 — % Excise tax expense (659) (818) 159 (19) % Federal and state income and other tax expenses (2,814) (4,333) 1,519 (35) % Net investment income 90,324 88,183 2,141 2 % Net realized gain 32,828 52,420 (19,592) NM Net unrealized appreciation (depreciation) 32,220 (18,951) 51,171 NM Income tax benefit (provision) on net realized gain and net unrealized appreciation (depreciation) (7,795) 882 (8,677) NM Net increase in net assets resulting from operations $ 147,577 $ 122,534 $ 25,043 20 % Three Months Ended June 30, Net Change 2026 2025 Amount % (dollars in thousands, except per share amounts) Net investment income $ 90,324 $ 88,183 $ 2,141 2 % Share‑based compensation expense 5,807 5,416 391 7 % Deferred compensation expense 1,261 745 516 NM Distributable net investment income (a) $ 97,392 $ 94,344 $ 3,048 3 % Excise tax expense 659 818 (159) (19) % Federal and state income and other tax expenses 2,814 4,333 (1,519) (35) % Distributable net investment income before taxes (b) $ 100,865 $ 99,495 $ 1,370 1 % Net investment income per share—Basic and diluted $ 0.97 $ 0.99 $ (0.02) (2) % Distributable net investment income per share—Basic and diluted (a) $ 1.04 $ 1.06 $ (0.02) (2) % Distributable net investment income before taxes per share—Basic and diluted (b) $ 1.08 $ 1.11 $ (0.03) (3) % ___________________________ NM — Net Change % not meaningful (a)Distributable net investment income is net investment income as determined in accordance with U.S. GAAP, excluding the impact of share-based compensation expense and deferred compensation expense or benefit. We believe presenting distributable net investment income and the related per share amounts is useful and appropriate supplemental disclosure for analyzing our financial performance since (i) share-based compensation does not require settlement in cash and (ii) deferred compensation expense or benefit does not result in a net cash impact to Main Street upon settlement. However, distributable net investment income is a non-U.S. GAAP measure and should not be considered as a replacement for net investment income or other earnings measures presented in accordance with U.S. GAAP and should be reviewed only in connection with such U.S. GAAP measures in analyzing our financial performance. A reconciliation of net investment income in accordance with U.S. GAAP to distributable net investment income is detailed in the table above. 142 Table of contents (b)Distributable net investment income before taxes is net investment income as determined in accordance with U.S. GAAP, excluding the impact of share-based compensation expense, deferred compensation expense or benefit and any tax expenses included in net investment income. We believe presenting distributable net investment income before taxes and the related per share amounts is useful and appropriate supplemental disclosure for analyzing our financial performance since (i) share-based compensation does not require settlement in cash, (ii) deferred compensation expense or benefit does not result in a net cash impact to Main Street upon settlement and (iii) tax expenses included in net investment income may include (a) excise tax expense, which is not solely attributable to net investment income, and (b) deferred taxes, which are not payable in the current period. However, distributable net investment income before taxes is a non-U.S. GAAP measure and should not be considered as a replacement for net investment income, net investment income before taxes or other earnings measures presented in accordance with U.S. GAAP and should be reviewed only in connection with such U.S. GAAP measures in analyzing our financial performance. A reconciliation of net investment income in accordance with U.S. GAAP to distributable net investment income before taxes is detailed in the table above. Investment Income Total investment income for the three months ended June 30, 2026 was $149.6 million, a 4% increase from the $144.0 million for the corresponding period of 2025. A summary of the changes in the comparable period activity is as follows: Three Months Ended June 30, Net Change 2026 2025 Amount % (dollars in thousands) Interest income $ 112,633 $ 100,857 $ 11,776 12 % (a) Dividend income 27,398 37,845 (10,447) (28) % (b) Fee income 9,541 5,271 4,270 81 % (c) Total investment income $ 149,572 $ 143,973 $ 5,599 4 % (d) ___________________________ (a)The increase in interest income was primarily attributable to higher average levels of income producing Investment Portfolio debt investments, partially offset by (i) a decrease in interest rates, primarily resulting from decreases in benchmark index interest rates on floating rate Investment Portfolio debt investments, and (ii) the negative impact from Investment Portfolio debt investments on non-accrual status. (b)The decrease in dividend income was primarily a result of dividend income decreases of (i) $8.8 million from our LMM portfolio companies, (ii) $0.8 million from our External Investment Manager and (iii) $0.5 million from our Other Portfolio investments. (c)The increase in fee income was primarily due to increases of (i) $2.8 million from increased refinancing and prepayment of Investment Portfolio debt investments and (ii) $1.5 million related to increased investment activity. (d)The increase in total investment income includes a net increase of $1.4 million in certain income considered less consistent or non-recurring, including increases of (i) $3.1 million in such fee income and (ii) $0.8 million in such interest income from accelerated prepayment, repricing and other activity related to certain Investment Portfolio debt investments, partially offset by a decrease of $2.5 million in such dividend income. 143 Table of contents Expenses Total expenses for the three months ended June 30, 2026 were $55.8 million, a 10% increase from the $50.6 million in the corresponding period of 2025. A summary of the changes in the comparable period activity is as follows: Three Months Ended June 30, Net Change 2026 2025 Amount % (dollars in thousands) Cash compensation $ 12,978 $ 11,932 $ 1,046 9 % (a) Deferred compensation expense 1,261 745 516 NM Compensation 14,239 12,677 1,562 12 % General and administrative 5,718 5,919 (201) (3) % Interest 36,637 32,519 4,118 13 % (b) Share-based compensation 5,807 5,416 391 7 % Gross expenses 62,401 56,531 5,870 10 % Expenses allocated to the External Investment Manager (6,626) (5,892) (734) 12 % (c) Total expenses $ 55,775 $ 50,639 $ 5,136 10 % ___________________________ NM — Net Change % not meaningful (a)The increase in cash compensation was primarily attributable to increases in employee headcount to support our growing Investment Portfolio and asset management activities, base compensation rates and other compensation related accruals. (b)The increase in interest expense was primarily related to an increase in average borrowings outstanding used to fund a portion of the growth of our Investment Portfolio, partially offset by a decreased weighted-average interest rate on our Credit Facilities (as defined in the Liquidity and Capital Resources section below) due to decreases in benchmark index rates. (c)The increase in expenses allocated to the External Investment Manager was primarily driven by the increased compensation expenses. Net Investment Income Net investment income for the three months ended June 30, 2026 increased 2% to $90.3 million, or $0.97 per share, compared to $88.2 million, or $0.99 per share, in the corresponding period of 2025. The increase in net investment income is the result of (i) the increase in total investment income, as discussed above, and (ii) the decrease in net investment income related tax expenses, as discussed below, partially offset by the increase in the total expenses, as discussed above. The decrease in net investment income per share reflects the increase in net investment income after the impact of the increase in weighted-average shares outstanding for the three months ended June 30, 2026, primarily due to shares issued since the beginning of the comparable period of the prior year through our (i) at-the-market offering program (the “ATM Program”), (ii) dividend reinvestment plan (“DRIP”) and (iii) equity incentive compensation plans. The decrease in net investment income on a per share basis is after a net increase of $0.01 per share resulting from an increase in investment income considered less consistent or non-recurring in nature, as discussed above. Distributable Net Investment Income Distributable net investment income for the three months ended June 30, 2026 increased 3% to $97.4 million, or $1.04 per share, compared to $94.3 million, or $1.06 per share, in the corresponding period of 2025. The increase in distributable net investment income was primarily due to the increase in net investment income, as discussed above, excluding the negative impact of the increases in (i) deferred compensation expense and (ii) share-based compensation expense. The decrease in distributable net investment income per share reflects the increase in distributable net investment income after the impact of the increase in weighted-average shares outstanding for the three months ended June 30, 2026, as discussed above. The decrease in distributable net investment income on a per share basis is after a $0.01 per share increase in investment income considered less consistent or non-recurring in nature, as discussed above. 144 Table of contents Net Realized Gain A summary of the primary components of the total net realized gain on investments of $32.8 million for the three months ended June 30, 2026 is as follows: Three Months Ended June 30, 2026 Full Exits Partial Exits Restructures Other (a) Total Net Gain/(Loss) # of Portfolio Companies Net Gain/(Loss) # of Portfolio Companies Net Gain/(Loss) # of Portfolio Companies Net Gain/(Loss) Net Gain/(Loss) (dollars in thousands) LMM portfolio $ 46,401 1 $ — — $ — — $ (250) $ 46,151 Private Loan portfolio — — — — (13,282) 1 420 (12,862) Middle Market portfolio — — — — — — — — Other Portfolio — — — — — — (461) (461) Total net realized gain (loss) $ 46,401 1 $ — — $ (13,282) 1 $ (291) $ 32,828 ___________________________ (a)Other activity includes realized gains and losses from transactions involving 14 portfolio companies which are not considered to be significant individually or in the aggregate. Net Unrealized Appreciation A summary of the total net unrealized appreciation of $32.2 million for the three months ended June 30, 2026 is as follows: Three Months Ended June 30, 2026 LMM (a) Private Loan Middle Market Other Total (in thousands) Accounting reversals of net unrealized (appreciation) depreciation recognized in prior periods due to net realized (gains / income) losses recognized during the current period $ (47,202) $ 11,052 $ — $ 461 $ (35,689) Net unrealized appreciation (depreciation) relating to portfolio investments 54,757 20,211 (487) (6,572) (b) 67,909 Total net unrealized appreciation (depreciation) relating to portfolio investments $ 7,555 $ 31,263 $ (487) $ (6,111) $ 32,220 ___________________________ (a)Includes unrealized appreciation on 38 LMM portfolio investments and unrealized depreciation on 28 LMM portfolio investments. (b)Includes $7.9 million of unrealized depreciation related to the External Investment Manager. Income Taxes Main Street’s income taxes include excise tax expense at MSCC and federal and state income and other tax expenses at the Taxable Subsidiaries. MSCC has elected to be treated for U.S. federal income tax purposes as a RIC. MSCC’s taxable income includes the taxable income generated by MSCC and certain of its subsidiaries, including the Funds and Structured Subsidiaries, which are treated as disregarded entities for tax purposes. As a result of its investment activities and dividend policy and activities, MSCC incurs federal excise tax on its estimated undistributed taxable income. The Taxable Subsidiaries incur federal and state income and other taxes related to net investment income resulting from the Taxable Subsidiaries’ investment activities. The excise tax expense decrease for the three months ended June 30, 2026 when compared to the prior year is due to a reduction in our estimated undistributed taxable income at MSCC, which is taxed at a 4% rate. The net investment income related federal and state income and other tax expenses decrease for the three months ended June 30, 2026 when compared to the prior year is due to decreases in taxable net investment income at the Taxable Subsidiaries. The Taxable Subsidiaries also incur taxes on realized gains (losses) and unrealized appreciation (depreciation). These taxes will change over time due to changes in the valuations of portfolio investments and realized gains and losses, in each case, on our investments owned by the Taxable Subsidiaries. 145 Table of contents Net Increase in Net Assets Resulting from Operations The net increase in net assets resulting from operations for the three months ended June 30, 2026 increased 20% to $147.6 million, or $1.58 per share, compared to $122.5 million, or $1.37 per share, for the three months ended June 30, 2025. The tables above provide a summary of the reasons for the change in net increase in net assets resulting from operations for the three months ended June 30, 2026 as compared to the three months ended June 30, 2025. Comparison of the six months ended June 30, 2026 and 2025 Set forth below is a comparison of the results of operations, and a reconciliation of net investment income to distributable net investment income and distributable net investment income before taxes for the six months ended June 30, 2026 and 2025. Six Months Ended June 30, Net Change 2026 2025 Amount % (dollars in thousands) Total investment income $ 289,678 $ 281,019 $ 8,659 3 % Total expenses (108,038) (97,875) (10,163) 10 % Net investment income before taxes 181,640 183,144 (1,504) (1) % Excise tax expense (1,040) (2,159) 1,119 (52) % Federal and state income and other tax expenses (5,697) (6,905) 1,208 (17) % Net investment income 174,903 174,080 823 — % Net realized gain 50,801 22,875 27,926 NM Net unrealized appreciation (depreciation) (18,379) 44,239 (62,618) NM Income tax provision on net realized gain and net unrealized appreciation (depreciation) (10,767) (2,578) (8,189) NM Net increase in net assets resulting from operations $ 196,558 $ 238,616 $ (42,058) (18) % Six Months Ended June 30, Net Change 2026 2025 Amount % (dollars in thousands, except per share amounts) Net investment income $ 174,903 $ 174,080 $ 823 — % Share‑based compensation expense 10,912 10,258 654 6 % Deferred compensation expense 2,363 925 1,438 NM Distributable net investment income (a) $ 188,178 $ 185,263 $ 2,915 2 % Excise tax expense 1,040 2,159 (1,119) (52) % Federal and state income and other tax expenses 5,697 6,905 (1,208) (17) % Distributable net investment income before taxes (b) $ 194,915 $ 194,327 $ 588 — % Net investment income per share—Basic and diluted $ 1.90 $ 1.96 $ (0.06) (3) % Distributable net investment income per share—Basic and diluted (a) $ 2.05 $ 2.08 $ (0.03) (1) % Distributable net investment income before taxes per share—Basic and diluted (b) $ 2.12 $ 2.18 $ (0.06) (3) % ____________________ NM — Net change % not meaningful (a)Distributable net investment income is net investment income as determined in accordance with U.S. GAAP, excluding the impact of share-based compensation expense and deferred compensation expense or benefit. We believe presenting distributable net investment income and the related per share amounts is useful and appropriate supplemental disclosure for analyzing our financial performance since (i) share-based compensation does not require settlement in cash and (ii) deferred compensation expense or benefit does not result in a net cash impact to Main Street upon settlement. However, distributable net investment income is a non-U.S. GAAP measure and should not be considered as a replacement for net investment income or other earnings measures presented in accordance with U.S. GAAP and should be reviewed only in connection with such U.S. GAAP measures in analyzing our financial performance. A reconciliation of net investment income in accordance with U.S. GAAP to distributable net investment income is detailed in the table above. 146 Table of contents (b)Distributable net investment income before taxes is net investment income as determined in accordance with U.S. GAAP, excluding the impact of share-based compensation expense, deferred compensation expense or benefit and any tax expenses included in net investment income. We believe presenting distributable net investment income before taxes and the related per share amounts is useful and appropriate supplemental disclosure for analyzing our financial performance since (i) share-based compensation does not require settlement in cash, (ii) deferred compensation expense or benefit does not result in a net cash impact to Main Street upon settlement and (iii) tax expenses included in net investment income may include (a) excise tax expense, which is not solely attributable to net investment income, and (b) deferred taxes, which are not payable in the current period. However, distributable net investment income before taxes is a non-U.S. GAAP measure and should not be considered as a replacement for net investment income, net investment income before taxes or other earnings measures presented in accordance with U.S. GAAP and should be reviewed only in connection with such U.S. GAAP measures in analyzing our financial performance. A reconciliation of net investment income in accordance with U.S. GAAP to distributable net investment income before taxes is detailed in the table above. Investment Income Total investment income for the six months ended June 30, 2026 was $289.7 million, a 3% increase from the $281.0 million for the corresponding period of 2025. A summary of the changes in the comparable period activity is as follows: Six Months Ended June 30, Net Change 2026 2025 Amount % (dollars in thousands) Interest income $ 217,939 $ 198,874 $ 19,065 10 % (a) Dividend income 55,594 73,871 (18,277) (25) % (b) Fee income 16,145 8,274 7,871 95 % (c) Total investment income $ 289,678 $ 281,019 $ 8,659 3 % (d) ____________________ (a)The increase in interest income was primarily attributable to higher average levels of income producing Investment Portfolio debt investments, partially offset by (i) a decrease in interest rates, primarily resulting from decreases in benchmark index interest rates on floating rate Investment Portfolio debt investments, and (ii) the negative impact from Investment Portfolio debt investments on non-accrual status. (b)The decrease in dividend income was primarily a result of decreases of (i) $16.9 million from our LMM portfolio companies and (ii) $1.0 million from our Private Loan portfolio companies. (c)The increase in fee income was primarily due to increases of (i) $4.1 million related to increased investment activity and (ii) $3.8 million from increased refinancing and repayment of Investment Portfolio debt investments. (d)The increase in total investment income includes a net increase of $3.1 million in certain income considered less consistent or non-recurring, including increases of (i) $4.1 million increase in such fee income and (ii) $0.9 million in such interest income from accelerated prepayment, repricing and other activity related to certain Investment Portfolio debt investments, partially offset by a decrease of $1.8 million in such dividend income. 147 Table of contents Expenses Total expenses for the six months ended June 30, 2026 were $108.0 million, a 10% increase from the $97.9 million in the corresponding period of 2025. A summary of the changes in the comparable period activity is as follows: Six Months Ended June 30, Net Change 2026 2025 Amount % (dollars in thousands) Cash compensation $ 25,061 $ 23,228 $ 1,833 8 % (a) Deferred compensation expense 2,363 925 1,438 NM Compensation 27,424 24,153 3,271 14 % General and administrative 11,114 11,005 109 1 % Interest 70,680 63,687 6,993 11 % (b) Share-based compensation 10,912 10,258 654 6 % Gross expenses 120,130 109,103 11,027 10 % Expenses allocated to the External Investment Manager (12,092) (11,228) (864) 8 % Total expenses $ 108,038 $ 97,875 $ 10,163 10 % ____________________ NM — Net Change % not meaningful (a)The increase in cash compensation was primarily attributable to increases in employee headcount to support our growing Investment Portfolio and asset management activities, base compensation rates and other compensation related accruals. (b)The increase in interest expense was primarily related to an increase in average borrowings outstanding used to fund a portion of the growth of our Investment Portfolio, partially offset by a decreased weighted-average interest rate on our Credit Facilities due to decreases in benchmark index rates and a decreased weighted-average interest rate on our unsecured debt borrowings as a result of borrowing and refinancing activities. Net Investment Income Net investment income for the six months ended June 30, 2026 increased 0.5% to $174.9 million, or $1.90 per share, compared to $174.1 million, or $1.96 per share, in the corresponding period of 2025. The increase in net investment income is the result of (i) the increase in total investment income, as discussed above, and (ii) the decrease in net investment income related tax expenses, as discussed below, partially offset by the increase in the total expenses, as discussed above. The decrease in net investment income per share reflects the increase in net investment income after the impact of the increase in weighted-average shares outstanding for the six months ended June 30, 2026, primarily due to shares issued since the beginning of the comparable period of the prior year through our (i) ATM Program, (ii) DRIP and (iii) equity incentive compensation plans. The decrease in net investment income on a per share basis is after a net increase of $0.02 per share resulting from items considered less consistent or non-recurring in nature, including a $0.03 per share increase in such investment income, as discussed above, partially offset by a $0.01 per share increase in deferred compensation expenses. Distributable Net Investment Income Distributable net investment income for the six months ended June 30, 2026 increased 2% to $188.2 million, or $2.05 per share, compared to $185.3 million, or $2.08 per share, in the corresponding period of 2025. The increase in distributable net investment income was primarily due to the increase in net investment income, as discussed above, excluding the negative impact of increases in (i) deferred compensation expense and (ii) share-based compensation expense. The decrease in distributable net investment income per share reflects the increase in distributable net investment income after the impact of the increase in weighted-average shares outstanding for the six months ended June 30, 2026, as discussed above. The decrease in distributable net investment income on a per share basis is after a $0.03 per share increase in investment income considered less consistent or non-recurring in nature, as discussed above. 148 Table of contents Net Realized Gain A summary of the primary components of the total net realized gain on investments of $50.8 million for the six months ended June 30, 2026 is as follows: Six Months Ended June 30, 2026 Full Exits Partial Exits Restructures Other (a) Total Net Gain/(Loss) # of Portfolio Companies Net Gain/(Loss) # of Portfolio Companies Net Gain/(Loss) # of Portfolio Companies Net Gain/(Loss) Net Gain/(Loss) (dollars in thousands) LMM portfolio $ 62,140 3 $ — — $ — — $ (289) $ 61,851 Private Loan portfolio 23 3 — — (13,282) 1 820 (12,439) Middle Market portfolio — — — — — — 1 1 Other Portfolio — — 1,849 2 — — (461) 1,388 Total net realized gain (loss) $ 62,163 6 $ 1,849 2 $ (13,282) 1 $ 71 $ 50,801 ____________________ (a)Other activity includes realized gains and losses from transactions involving 17 portfolio companies which are not considered to be significant individually or in the aggregate. Net Unrealized Depreciation A summary of the total net unrealized depreciation of $18.4 million for the six months ended June 30, 2026 is as follows: Six Months Ended June 30, 2026 LMM (a) Private Loan Middle Market Other Total (in thousands) Accounting reversals of net unrealized (appreciation) depreciation recognized in prior periods due to net realized (gains / income) losses recognized during the current period $ (63,890) $ 10,161 $ — $ (1,388) $ (55,117) Net unrealized appreciation (depreciation) relating to portfolio investments 84,059 (15,740) (3,403) (28,178) (b) 36,738 Total net appreciation (depreciation) relating to portfolio investments $ 20,169 $ (5,579) $ (3,403) $ (29,566) $ (18,379) ____________________ (a)Includes unrealized appreciation on 42 LMM portfolio investments and unrealized depreciation on 34 LMM portfolio investments. (b)Includes $29.8 million of unrealized depreciation related to the External Investment Manager. Income Taxes Main Street’s income taxes include excise tax expense at MSCC and federal and state income and other tax expenses at the Taxable Subsidiaries. MSCC has elected to be treated for U.S. federal income tax purposes as a RIC. MSCC’s taxable income includes the taxable income generated by MSCC and certain of its subsidiaries, including the Funds and Structured Subsidiaries, which are treated as disregarded entities for tax purposes. As a result of its investment activities and dividend policy and activities, MSCC incurs federal excise tax on its estimated undistributed taxable income. The Taxable Subsidiaries incur federal and state income and other taxes related to net investment income resulting from the Taxable Subsidiaries’ investment activities. The excise tax expense decrease for the six months ended June 30, 2026 when compared to the prior year is due to a reduction in our estimated undistributed taxable income at MSCC, which is taxed at a 4% rate. The net investment income related federal and state income and other tax expenses decrease for the six months ended June 30, 2026 when compared to the prior year is due to decreases in taxable net investment income at the Taxable Subsidiaries. The Taxable Subsidiaries also incur taxes on realized gains (losses) and unrealized appreciation (depreciation). These taxes will change over time due to changes in the valuations of portfolio investments and realized gains and losses, in each case, on our investments owned by the Taxable Subsidiaries. 149 Table of contents Net Increase in Net Assets Resulting from Operations The net increase in net assets resulting from operations for the six months ended June 30, 2026 was $196.6 million, or $2.14 per share, compared to $238.6 million, or $2.68 per share, for the six months ended June 30, 2025. The tables above provide a summary of the reasons for the change in net increase in net assets resulting from operations for the six months ended June 30, 2026 as compared to the six months ended June 30, 2025. LIQUIDITY AND CAPITAL RESOURCES Cash Flows For the six months ended June 30, 2026, we realized a net increase in cash and cash equivalents of $16.3 million, which is the net result of $22.0 million of cash used in our operating activities and $38.3 million of cash provided by our financing activities. The $22.0 million of cash used in our operating activities resulted primarily from (i) cash uses totaling $733.2 million for the funding of new and follow-on portfolio investments and (ii) $11.5 million in net cash uses related to other assets and liabilities, partially offset by (i) cash proceeds totaling $551.8 million from the repayments of debt investments and sales of and return of capital from equity investments and (ii) cash flows that we generated from the operating profits earned totaling $173.6 million, which is our distributable net investment income, excluding the non-cash effects of net investment income related deferred taxes, the accretion of unearned income, PIK interest income, cumulative dividends and the amortization expense for deferred financing costs. The $38.3 million of cash provided by our financing activities principally consisted of (i) $200.0 million in cash proceeds from the issuance of additional aggregate principal amount of the March 2029 Notes (as defined below), (ii) $153.2 million in net cash proceeds from equity offerings from our ATM Program and (iii) $150.0 million in cash proceeds from the issuance of aggregate principal amount of the April 2031 Notes (as defined below), partially offset by (i) $277.0 million in net repayments from our Credit Facilities, (ii) $177.8 million in dividends paid to our stockholders, (iii) $9.0 million in purchases of vested stock for employee payroll tax withholdings and (iv) $1.1 million for the payment of debt issuance costs. Capital Resources As of June 30, 2026, we had $58.3 million in cash and cash equivalents and $1.095 billion of unused capacity, which is after a reduction of $500.0 million to provide for the scheduled repayment of the July 2026 Notes (as defined below) at maturity, under our Credit Facilities, which we maintain to support our investment and operating activities. As of June 30, 2026, our NAV totaled $3.2 billion, or $33.92 per share. In June 2026, we entered into an amendment to our multi-year revolving credit facility (the “Corporate Facility”), to among other things: (i) increase the revolving commitments to $1.240 billion, (ii) increase the accordion feature providing us with the right to request increases in commitments under the facility from new and existing lenders on the same terms and conditions as the existing commitments to up to a total of $1.860 billion and (iii) extend the revolving period and final maturity date through June 2030 and to June 2031, respectively. As of June 30, 2026, we had $26.0 million outstanding and $710.1 million of undrawn commitments under our Corporate Facility, which is after a reduction of $500.0 million to provide for the scheduled repayment of the July 2026 Notes at maturity, and we, through MSCC Funding, had $215.0 million outstanding and $385.0 million of undrawn commitments under our special purpose vehicle revolving credit facility (the “SPV Facility” and, together with the Corporate Facility, the “Credit Facilities”), both of which approximated fair value. Availability under our Credit Facilities is subject to certain leverage and borrowing base limitations, covenants, reporting and other requirements customary for similar credit facilities. For further information on our Credit Facilities, including key terms and financial covenants, refer to Note E — Debt in the notes to the consolidated financial statements included in Item 1. Consolidated Financial Statements of this Quarterly Report on Form 10-Q. In January 2024, we issued $350.0 million in aggregate principal amount of 6.95% unsecured notes due March 1, 2029 (the “March 2029 Notes”). In March 2026, we issued an additional $200.0 million in aggregate principal amount of the March 2029 Notes at a public offering price of 102.061% resulting in a yield-to-worst of 6.164% on such issuance. The March 2029 Notes issued in March 2026 have identical terms as, and are a part of a single series with, the March 2029 Notes issued in January 2024. The outstanding aggregate principal amount of the March 2029 Notes was $550.0 million and $350.0 million as of June 30, 2026 and December 31, 2025, respectively. The $550.0 million of outstanding March 2029 Notes bear interest at 6.95% per year with a yield-to-maturity of 6.68% as of June 30, 2026. 150 Table of contents In January 2021, we issued $300.0 million in aggregate principal amount of 3.00% unsecured notes due July 14, 2026 (the “July 2026 Notes”). In October 2021, we issued an additional $200.0 million in aggregate principal amount of the July 2026 Notes. The outstanding aggregate principal amount of the July 2026 Notes was $500.0 million as of both June 30, 2026 and December 31, 2025. In July 2026, we repaid the entire $500.0 million in aggregate principal amount of the July 2026 Notes at maturity at par value plus the accrued and unpaid interest. In June 2024, we issued $300.0 million in aggregate principal amount of 6.50% unsecured notes due June 4, 2027 (the “June 2027 Notes”). In September 2024, we issued an additional $100.0 million in aggregate principal amount of the June 2027 Notes at a public offering price of 102.134% resulting in a yield-to-maturity of 5.617% on such issuance. The June 2027 Notes issued in September 2024 have identical terms as, and are a part of a single series with, the June 2027 Notes issued in June 2024. The outstanding aggregate principal amount of the June 2027 Notes was $400.0 million and bear interest at a rate of 6.50% per year with a yield-to-maturity of approximately 6.34% as of both June 30, 2026 and December 31, 2025. In August 2025, we issued $350.0 million in aggregate principal amount of 5.40% unsecured notes due August 15, 2028 (the “August 2028 Notes”). The outstanding aggregate principal amount of the August 2028 Notes was $350.0 million as of both June 30, 2026 and December 31, 2025. Through the Funds, we have the ability to issue SBIC debentures guaranteed by the SBA at favorable interest rates and favorable terms and conditions. Under previous SBIC regulations, SBA-approved SBICs under common control had the ability to issue debentures guaranteed by the SBA up to a regulatory maximum amount of $350.0 million. In May 2026, the Investing in All of America Act was enacted, increasing the maximum leverage available to commonly controlled SBICs. This allows access to an additional $125.0 million of SBIC debenture capacity above the previous $350.0 million maximum, bringing total potential capacity to $475.0 million. Under existing SBA-approved commitments, we, through the Funds, had $350.0 million of outstanding SBIC debentures guaranteed by the SBA as of June 30, 2026, which bear a weighted-average annual fixed interest rate of 3.3%, paid semiannually, and mature ten years from issuance. The first maturity related to our SBIC debentures occurs in March 2027, and the weighted-average remaining duration is 4.1 years as of June 30, 2026. Debentures guaranteed by the SBA have fixed interest rates that equal prevailing 10-year Treasury Note rates plus a market spread and have a maturity of ten years with interest payable semiannually. The principal amount of the debentures is not required to be paid before maturity, but may be pre-paid at any time with no prepayment penalty. We expect to maintain SBIC debentures under the SBIC program in the future, subject to periodic repayments and borrowings, in an amount up to the regulatory maximum amount for affiliated SBIC funds. In April 2026, we issued $150.0 million in aggregate principal amount of 6.93% Series A Senior Notes due April 15, 2031 (the “April 2031 Notes”). The outstanding aggregate principal amount of the April 2031 Notes was $150.0 million as of June 30, 2026. In September 2025, we repaid the entire $100.0 million principal amount of the issued and outstanding 7.84% unsecured notes and the entire $50.0 million principal amount of the issued and outstanding 7.53% unsecured notes (collectively, the “December 2025 Notes”) prior to maturity at par value plus the accrued and unpaid interest. We maintain the ATM Program with certain selling agents through which we can sell up to 20,000,000 shares of our common stock by means of at-the-market offerings from time to time. During the six months ended June 30, 2026, we sold 2,790,683 shares of our common stock at a weighted-average price of $55.43 per share and raised $154.7 million of gross proceeds under the ATM Program, or net proceeds of $152.9 million after commissions to the selling agents on shares sold and offering costs. As of June 30, 2026, sales transactions representing 5,159 shares had not settled and thus were not issued and not included in shares issued and outstanding on the face of the Consolidated Balance Sheets, but are included as outstanding on the Consolidated Statement of Changes in Net Assets, in the weighted-average shares outstanding in the Consolidated Statements of Operations and in the shares used to calculate the NAV per share. As of June 30, 2026, 16,740,256 shares remained available for sale under the ATM Program. During the year ended December 31, 2025, we sold 540,423 shares of our common stock at a weighted-average price of $59.01 per share and raised $31.9 million of gross proceeds under the ATM Program. Net proceeds were $31.3 million after commissions to the selling agents on shares sold and offering costs. We anticipate that we will continue to fund our investment activities through existing cash and cash equivalents, cash flows generated through our ongoing operating activities, utilization of available borrowings under our Credit Facilities, and a combination of future issuances of debt and equity capital. Our primary uses of funds will be investments in portfolio companies, operating expenses, cash distributions to holders of our common stock and repayments of note and debenture obligations as they come due. 151 Table of contents We periodically invest excess cash balances into marketable securities and short-term investments. The primary investment objective of marketable securities and short-term investments is to generate incremental cash returns on excess cash balances prior to utilizing those funds for investment in our LMM and Private Loan portfolio investments. Marketable securities generally consist of money market funds and certificates of deposit with financial institutions. Short-term portfolio investments consist primarily of investments in secured debt investments and independently rated debt investments. If our common stock trades below our NAV per share, we will generally not be able to issue additional common stock at the market price, unless our stockholders approve such a sale and our Board of Directors makes certain determinations. We did not seek stockholder authorization to sell shares of our common stock below the then current NAV per share of our common stock at our 2026 Annual Meeting of Stockholders, and have not sought such authorization since 2012, because our common stock price per share has generally traded significantly above the NAV per share of our common stock since 2011, except for a brief period during market disruptions related to the COVID-19 pandemic. We would therefore need future approval from our stockholders to issue shares below the then current NAV per share. In order to satisfy the Code requirements applicable to a RIC, we intend to distribute to our stockholders, after consideration and application of our ability under the Code to carry forward certain excess undistributed taxable income from one tax year into the next tax year, substantially all of our taxable income. In accordance with the 1940 Act, we are allowed to borrow amounts such that our asset coverage ratio, or BDC asset coverage ratio, of our total assets to our total senior securities, which includes borrowings and any preferred stock we may issue in the future, is at least 150% after such borrowing. In January 2008, we received exemptive relief from the SEC to exclude SBA-guaranteed debt securities issued by the Funds and any other wholly-owned subsidiaries of ours which operate as SBICs from the BDC asset coverage ratio which, in turn, enables us to fund more investments with debt capital. Upon receipt of stockholder approval in accordance with the 1940 Act, our BDC asset coverage ratio requirement was reduced from 200% to 150% effective May 3, 2022. As of June 30, 2026, our BDC asset coverage ratio was 244%. Although we have been able to secure access to additional liquidity, including through our Credit Facilities, public and private debt issuances, leverage available through the SBIC program and equity offerings, there is no assurance that debt or equity capital will be available to us in the future on favorable terms, or at all. Recently Issued or Adopted Accounting Standards From time to time, new accounting pronouncements are issued by the FASB or other standards-setting bodies that are adopted by us as of the specified effective date. We believe that the impact of recently issued standards and any that are not yet effective will not have a material impact on our consolidated financial statements upon adoption. For a description of recently issued or adopted accounting standards, see Note B.15. — Summary of Significant Accounting Policies — Recently Issued or Adopted Accounting Standards in the notes to the consolidated financial statements included in Item 1. Consolidated Financial Statements of this Quarterly Report on Form 10-Q. Inflation Inflation has not historically had a significant effect on our results of operations in any of the reporting periods presented herein. However, our portfolio companies have experienced, specifically including over the last few years, as a result of recent geopolitical events, uncertainty with respect to the imposition of tariffs on and trade disputes with certain countries, supply chain and labor issues, and may continue to experience, the increasing impacts of inflation on their operating results, including periodic escalations in their costs for labor, raw materials and third-party services and required energy consumption. These issues and challenges related to inflation are receiving significant attention from our investment teams and the management teams of our portfolio companies as we work to manage these growing challenges. Prolonged or more severe impacts of inflation to our portfolio companies could continue to affect their operating profits and, thereby, increase their borrowing costs, and as a result negatively impact their ability to service their debt obligations and/or reduce their available cash for distributions. In addition, these factors could have a negative effect on the fair value of our investments in these portfolio companies. The combined impacts therefrom in turn could negatively affect our results of operations. Off-Balance Sheet Arrangements We may be a party to financial instruments with off-balance sheet risk in the normal course of business to meet the financial needs of our portfolio companies. These instruments include commitments to extend credit and fund equity capital and involve, to varying degrees, elements of liquidity and credit risk in excess of the amount recognized in the Consolidated Balance Sheets. As of June 30, 2026, we had a total of $395.4 million in outstanding commitments comprised of (i) 73 investments with commitments to fund revolving loans that had not been fully drawn or term loans with additional commitments not yet funded and (ii) 11 investments with equity capital commitments that had not been fully called. 152 Table of contents Contractual Obligations As of June 30, 2026, the future commitments for cash payments in connection with our Credit Facilities, the March 2029 Notes, the July 2026 Notes, the June 2027 Notes, the August 2028 Notes, SBIC debentures, the April 2031 Notes and rent obligations under our office lease for each of the next five years and thereafter are as follows: 2026 2027 2028 2029 2030 Thereafter Total (in thousands) Corporate Facility (1) $ — $ — $ — $ — $ — $ 26,000 $ 26,000 SPV Facility (1) — — — — 215,000 — 215,000 March 2029 Notes — — — 550,000 — — 550,000 Interest due on March 2029 Notes 19,113 38,225 38,225 19,113 — — 114,676 July 2026 Notes 500,000 — — — — — 500,000 Interest due on July 2026 Notes 7,500 — — — — — 7,500 June 2027 Notes — 400,000 — — — — 400,000 Interest due on June 2027 Notes 13,000 13,000 — — — — 26,000 August 2028 Notes — — 350,000 — — — 350,000 Interest due on August 2028 Notes 9,450 18,900 18,900 — — — 47,250 SBIC debentures — 75,000 75,000 — 35,000 165,000 350,000 Interest due on SBIC debentures 5,726 10,651 8,128 6,170 6,006 18,558 55,239 April 2031 Notes — — — — — 150,000 150,000 Interest due on April 2031 Notes 5,400 10,395 10,395 10,395 10,395 5,198 52,178 Operating Lease Obligation (2) 623 1,267 1,289 1,310 1,333 4,483 10,305 Total $ 560,812 $ 567,438 $ 501,937 $ 586,988 $ 267,734 $ 369,239 $ 2,854,148 ___________________________ (1)Future interest payments on our Credit Facilities have not been included, as these amounts fluctuate over time depending on the current interest rates and amounts outstanding. (2)Operating Lease Obligation means a rent payment obligation under a lease classified as an operating lease and disclosed pursuant to ASC 842, as may be modified or supplemented. Related Party Transactions and Agreements We have entered into agreements and transactions with the External Investment Manager, MSC Income, Private Loan Fund I and Private Loan Fund II, whereby we have made debt and equity investments and receive certain fees, expense reimbursements and investment income. See Note D — External Investment Manager and Note L — Related Party Transactions in the notes to the consolidated financial statements included in Item 1. Consolidated Financial Statements of this Quarterly Report on Form 10-Q for additional information regarding these related party transactions and agreements. In addition, Main Street’s Nonqualified Supplemental Deferred Compensation Plan (the “Deferred Compensation Plan”) allows non-employee directors and certain employees to defer receipt of some or all of their cash compensation or directors’ fees in accordance with the terms of the Deferred Compensation Plan. See Note B.9. — Summary of Significant Accounting Policies — Deferred Compensation Plan and Note L — Related Party Transactions in the notes to the consolidated financial statements included in Item 1. Consolidated Financial Statements of this Quarterly Report on Form 10-Q for additional information regarding the Deferred Compensation Plan. Recent Developments In August 2026, we declared a supplemental dividend of $0.30 per share payable in September 2026. This supplemental dividend is in addition to the previously announced regular monthly dividends that we declared of $0.265 per share for each month of July, August and September 2026 or total regular monthly dividends of $0.795 per share for the third quarter of 2026, resulting in total dividends declared for the third quarter of 2026 of $1.095 per share. In August 2026, we also declared regular monthly dividends of $0.265 per share for each month of October, November and December of 2026. These regular monthly dividends equal a total of $0.795 per share for the fourth quarter of 2026, representing a 3.9% increase from the regular monthly dividends paid in the fourth quarter of 2025. Including the regular monthly and supplemental dividends declared through the fourth quarter of 2026, we will have paid $51.205 per share in cumulative dividends since our October 2007 initial public offering. 153 Table of contents In August 2026, our Board of Directors authorized us to enter into a share purchase plan to purchase up to $20.0 million of shares of MSC Income’s common stock in the open market for a period beginning in September 2026 and ending in February 2027 at times when the market price per share of MSC Income’s common stock is trading below the most recently reported NAV per share of the common stock by certain pre-determined levels. The purchases of shares of MSC Income common stock pursuant to the share purchase plan are intended to satisfy the conditions of Rule 10b5-1 and Rule 10b-18 under the Exchange Act and will otherwise be subject to applicable law, including Regulation M, which may prohibit purchases under certain circumstances. MSC Income’s board of directors also authorized MSC Income to enter into a share repurchase plan to purchase up to $20.0 million of shares of its common stock, with the terms and conditions substantially similar between our share purchase plan for shares of MSC Income common stock and MSC Income’s share repurchase plan, and daily purchases under the two plans, if any, are expected to be split pro rata (or as close thereto as reasonably possible) between us and MSC Income based on the respective plan sizes.