Quarterly report [Sections 13 or 15(d)]

FAIR VALUE HIERARCHY FOR INVESTMENTS—PORTFOLIO COMPOSITION (Tables)

v3.26.1
FAIR VALUE HIERARCHY FOR INVESTMENTS—PORTFOLIO COMPOSITION (Tables)
 6 Months Ended
Jun. 30, 2026
Fair Value Disclosures [Abstract]  
Schedule of Fair Value Measurement Inputs and Valuation Techniques
A summary of the significant unobservable inputs used in the fair value measurement of Main Street’s Level 3 portfolio investments as of June 30, 2026 and December 31, 2025 is as follows:
Type of Investment
Fair Value as of June 30, 2026
(in thousands)
 Valuation Technique Significant Unobservable Inputs Range (4) Weighted-Average (4)(5) Median (4)
Equity investments $ 1,935,551  Discounted cash flow WACC
9.2% - 23.4%
 14.5% 15.1%
Market comparable / Enterprise value EBITDA multiple (1) (3)
4.3x - 9.4x (2)
 7.2x 6.8x
Debt investments $ 3,777,203  Discounted cash flow Risk adjusted discount rate (6)
7.9% - 18.0% (2)
 11.5% 11.3%
Expected principal recovery percentage
0.0% - 500.0%
 99.3% 100.0%
Debt investments $ 9,858  Market approach Third-party quote
14.5 - 78.5
 74.8 46.5
Total Level 3 investments $ 5,722,612 
___________________________
(1)EBITDA may include pro forma adjustments and/or other add-backs based on specific circumstances related to each investment.
(2)Range excludes outliers that are greater than one standard deviation from the mean. Including these outliers, the range for EBITDA multiple is 2.0x - 16.6x and the range for risk adjusted discount rate is 6.6% - 34.6%.
(3)The fair value determination of the equity investment in the External Investment Manager is based on a fee multiple of 7.4x, which represents a discounted, blended multiple based on (i) the multiples for similar businesses in active markets and (ii) actual multiples used in private transactions.
(4)Does not include investments for which the valuation technique does not include the use of the applicable fair value input.
(5)Weighted-Average is calculated for each significant unobservable input based on the applicable security’s fair value.
(6)Discount rate includes the effect of the standard SOFR base rate, as applicable.
Type of Investment
Fair Value as of December 31, 2025
(in thousands)
 Valuation Technique Significant Unobservable Inputs Range (4) Weighted-Average (4)(5) Median (4)
Equity investments $ 1,889,374  Discounted cash flow WACC
9.4% - 22.7%
 14.4% 15.0%
Market comparable / Enterprise value EBITDA multiple (1) (3)
5.0x - 9.0x (2)
 7.3x 6.5x
Debt investments $ 3,596,989  Discounted cash flow Risk adjusted discount rate (6)
8.0% - 18.3% (2)
 11.7% 11.5%
Expected principal recovery percentage
0.0% - 500.0%
 99.5% 100.0%
Debt investments $ 10,342  Market approach Third-party quote
14.5 - 63.0
 52.2 40.8
Total Level 3 investments $ 5,496,705 
___________________________
(1)EBITDA may include pro forma adjustments and/or other add-backs based on specific circumstances related to each investment.
(2)Range excludes outliers that are greater than one standard deviation from the mean. Including these outliers, the range for EBITDA multiple is 1.2x - 16.0x and the range for risk adjusted discount rate is 5.4% - 40.4%.
(3)The fair value determination of the equity investment in the External Investment Manager is based on a fee multiple of 7.8x, which represents a discounted, blended multiple based on (i) the multiples for similar businesses in active markets and (ii) actual multiples used in private transactions.
(4)Does not include investments for which the valuation technique does not include the use of the applicable fair value input.
(5)Weighted-Average is calculated for each significant unobservable input based on the applicable security’s fair value.
(6)Discount rate includes the effect of the standard SOFR base rate, as applicable.
Schedule of Changes in Fair Value of Main Street’s Level 3 Portfolio Investments
A summary of changes in the fair value of Main Street’s Level 3 portfolio investments for the six months ended June 30, 2026 and 2025 is as follows (in thousands):
Type of Investment
Fair Value as of December 31, 2025
 Transfers Into (Out of) Level 3 Hierarchy Redemptions/ Repayments New Investments Net Changes from Unrealized to Realized Net Unrealized Appreciation (Depreciation) Other (1)
Fair Value as of June 30, 2026
 Net Change in Unrealized Appreciation (Depreciation) for the Six Months Ended June 30, 2026 on Assets Still Held
Debt $ 3,607,331  $ —  $ (466,218) $ 686,358  $ 8,839  $ (44,338) $ (4,911) $ 3,787,061  $ (43,023)
Equity 1,858,205  —  (35,440) 60,490  (63,956) 81,832  4,911  1,906,042  72,824 
Equity Warrant 31,169  —  —  —  —  (1,660) —  29,509  (1,660)
$ 5,496,705  $ —  $ (501,658) $ 746,848  $ (55,117) $ 35,834  $ —  $ 5,722,612  $ 28,141 
___________________________
(1)Includes the impact of non-cash conversions. These transactions represent non-cash investing activities. See additional cash flow information in the Consolidated Statements of Cash Flows.
Type of Investment
Fair Value as of December 31, 2024
 Transfers Into (Out of) Level 3 Hierarchy Redemptions/ Repayments New Investments Net Changes from Unrealized to Realized Net Unrealized Appreciation (Depreciation) Other (1)
Fair Value as of June 30, 2025
 Net Change in Unrealized Appreciation (Depreciation) for the Six Months Ended June 30, 2025 on Assets Still Held
Debt $ 3,278,365  $ —  $ (514,216) $ 575,433  $ 38,415  $ (19,812) $ (30,773) $ 3,327,412  $ (9,904)
Equity 1,637,181  (16,810) (30,679) 80,309  (65,185) 83,449  30,773  1,719,038  18,553 
Equity Warrant 17,123  —  —  —  —  7,940  —  25,063  7,940 
$ 4,932,669  $ (16,810) $ (544,895) $ 655,742  $ (26,770) $ 71,577  $ —  $ 5,071,513  $ 16,589 
___________________________
(1)Includes the impact of non-cash conversions. These transactions represent non-cash investing activities. See additional cash flow information in the Consolidated Statements of Cash Flows.
Schedule of Portfolio Investments by Level in the Fair Value Hierarchy
As of June 30, 2026 and December 31, 2025, Main Street’s investments at fair value were categorized as follows in the fair value hierarchy for ASC 820 purposes:
Fair Value Measurements
(in thousands)
June 30, 2026
 Fair Value Quoted Prices in
Active Markets for
Identical Assets
(Level 1)		 Significant Other
Observable Inputs
(Level 2)		 Significant
Unobservable
Inputs
(Level 3)
LMM portfolio investments $ 3,205,604  $ —  $ —  $ 3,205,604 
Private Loan portfolio investments 2,090,873  —  —  2,090,873 
Middle Market portfolio investments 83,116  —  —  83,116 
Other Portfolio investments 141,251  23,432  —  117,819 
External Investment Manager 225,200  —  —  225,200 
Total investments $ 5,746,044  $ 23,432  $ —  $ 5,722,612 
Fair Value Measurements
(in thousands)
December 31, 2025
 Fair Value Quoted Prices in
Active Markets for
Identical Assets
(Level 1)		 Significant Other
Observable Inputs
(Level 2)		 Significant
Unobservable
Inputs
(Level 3)
LMM portfolio investments $ 3,057,023  $ —  $ —  $ 3,057,023 
Private Loan portfolio investments 1,988,438  —  —  1,988,438 
Middle Market portfolio investments 83,498  —  —  83,498 
Other Portfolio investments 134,138  21,412  —  112,726 
External Investment Manager 255,020  —  —  255,020 
Total investments $ 5,518,117  $ 21,412  $ —  $ 5,496,705 
Schedule of Investment Holdings
A summary of Main Street’s 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, Main Street had equity ownership in all of its 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 Main Street’s debt portfolio as of June 30, 2026, including debt investments on non-accrual status, was 12.1% for its LMM portfolio investments and 9.6% for its Private Loan portfolio investments. The weighted-average annual effective yield is not reflective of what an investor in shares of Main Street’s common stock will realize on their investment because it does not reflect changes in the market value of Main Street’s stock, Main Street’s utilization of debt capital in its capital structure, Main Street’s 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 Main Street’s 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.
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, Main Street had equity ownership in all of its 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 Main Street’s debt portfolio as of December 31, 2025, including debt investments on non-accrual status, was 12.0% for its LMM portfolio investments and 10.1% for its Private Loan portfolio investments. The weighted-average annual effective yield is not reflective of what an investor in shares of Main Street’s common stock will realize on their investment because it does not reflect changes in the market value of Main Street’s stock, Main Street’s utilization of debt capital in its capital structure, Main Street’s 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 Main Street’s 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.
The composition of Main Street’s 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  %
The composition of Main Street’s total combined LMM, Private Loan and Middle Market portfolio investments by geographic region of the U.S. and other countries at cost and fair value 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):
Cost: June 30, 2026 December 31, 2025
West 25.7  % 25.3  %
Midwest 21.6  19.2 
Southeast 18.1  17.5 
Southwest 17.2  19.0 
Northeast 14.1  15.4 
Canada 2.1  2.2 
Other Non-U.S. 1.2  1.4 
100.0  % 100.0  %
Fair Value: June 30, 2026 December 31, 2025
West 25.1  % 24.8  %
Midwest 22.3  20.1 
Southwest 20.5  23.0 
Southeast 16.8  15.8 
Northeast 12.3  13.1 
Canada 1.9  1.9 
Other Non-U.S. 1.1  1.3 
100.0  % 100.0  %
The composition of Main Street’s total combined LMM, Private Loan and Middle Market portfolio investments by industry at cost and fair value, as of June 30, 2026 and December 31, 2025, is as follows (this information excludes Other Portfolio investments and the External Investment Manager):
Cost: June 30, 2026 December 31, 2025
Construction & Engineering 8.6  % 6.1  %
Machinery 8.3  8.3 
Electrical Equipment 7.1  5.9 
Diversified Consumer Services 5.4  4.7 
Commercial Services & Supplies 5.2  6.8 
Distributors 4.9  5.0 
Professional Services 4.6  5.3 
Health Care Providers & Services 4.1  4.2 
Internet Software & Services 3.8  4.2 
Aerospace & Defense 3.8  2.3 
IT Services 3.2  3.7 
Containers & Packaging 3.2  3.3 
Auto Components 3.2  3.2 
Tobacco 2.4  2.5 
Textiles, Apparel & Luxury Goods 2.3  2.5 
Leisure Equipment & Products 2.1  2.1 
Computers & Peripherals 2.0  2.0 
Media 2.0  1.6 
Energy Equipment & Services 2.0  2.4 
Air Freight & Logistics 1.9  1.5 
Specialty Retail 1.9  2.0 
Software 1.9  2.1 
Communications Equipment 1.8  1.9 
Trading Companies & Distributors 1.5  1.8 
Food Products 1.4  1.4 
Chemicals 1.3  1.4 
Food & Staples Retailing 1.2  1.4 
Hotels, Restaurants & Leisure 1.0  1.1 
Oil, Gas & Consumable Fuels 1.0  1.1 
Internet & Catalog Retail 0.9  1.0 
Beverages 0.1  1.2 
Other (1) 5.9  6.0 
100.0  % 100.0  %
___________________________
(1)Includes various industries with each industry individually representing less than 1.0% of the total combined LMM, Private Loan and Middle Market portfolio investments at each date.
Fair Value: June 30, 2026 December 31, 2025
Machinery 10.0  % 10.2  %
Construction & Engineering 8.7  6.5 
Electrical Equipment 7.9  5.9 
Diversified Consumer Services 6.5  6.1 
Distributors 5.4  5.5 
Professional Services 4.6  5.2 
Commercial Services & Supplies 4.5  5.9 
Health Care Providers & Services 3.8  3.8 
Computers & Peripherals 3.8  3.6 
Aerospace & Defense 3.4  2.0 
Containers & Packaging 3.2  3.4 
Auto Components 3.1  3.0 
Internet Software & Services 3.0  3.4 
Tobacco 2.5  2.6 
IT Services 2.4  3.8 
Specialty Retail 2.3  2.4 
Software 2.1  2.2 
Media 2.0  1.6 
Energy Equipment & Services 1.9  2.5 
Textiles, Apparel & Luxury Goods 1.8  1.9 
Air Freight & Logistics 1.7  1.3 
Communications Equipment 1.6  1.7 
Leisure Equipment & Products 1.4  1.4 
Trading Companies & Distributors 1.4  1.6 
Chemicals 1.2  1.3 
Food Products 1.0  1.1 
Food & Staples Retailing 0.9  1.1 
Oil, Gas & Consumable Fuels 0.9  1.0 
Beverages 0.1  1.1 
Other (1) 6.9  6.9 
100.0  % 100.0  %
___________________________
(1)Includes various industries with each industry individually representing less than 1.0% of the total combined LMM, Private Loan and Middle Market portfolio investments at each date.