Business Interest Limitation: Definition and How IRC §163(j) Works

The business interest limitation is the rule under IRC §163(j) that caps the amount of business interest expense (BIE) a taxpayer may deduct in a given tax year. Deductible BIE is limited to the sum of: (1) the taxpayer's business interest income (BII) for the year; (2) floor plan financing interest (for vehicle and equipment dealers); and (3) 30% of adjusted taxable income (ATI). Any business interest expense that exceeds this cap is not permanently lost — it is disallowed for the current year and carried forward indefinitely to future tax years, where it remains subject to the same 30% limitation. The rule applies to virtually all taxpayers — individuals, partnerships, S-Corporations, and C-Corporations — except those qualifying for the small business exception.

Adjusted Taxable Income (ATI): The 30% Base

ATI is the denominator that drives the entire §163(j) calculation. The OBBBA (One Big Beautiful Bill Act, enacted July 4, 2025) permanently restored a more favorable EBITDA-based ATI computation for tax years beginning after December 31, 2024:

  • ATI = taxable income, adjusted by adding back: business interest expense, net operating loss deductions, the §199A (QBI) deduction, and — critically — depreciation, amortization, and depletion.
  • The depreciation/amortization addback is the key change. From 2022 through 2024, ATI was computed on an EBIT basis (no D&A addback), which dramatically reduced the deductible cap for capital-intensive businesses. A manufacturer with $5 million of annual depreciation who was trapped by EBIT-era ATI can now add that $5M back, raising the ATI base and potentially freeing up $1.5M of additional interest deduction (30% × $5M).

Businesses that accumulated §163(j) carryforwards during the 2022–2024 EBIT period can now utilize those deferred amounts faster under the expanded ATI base.

Small Business Exception

Taxpayers with average annual gross receipts of $31 million or less (2026 threshold, indexed for inflation) are fully exempt from §163(j) under the small business exception of §163(j)(3). These taxpayers deduct all business interest in full. The threshold is measured using the three-prior-year average gross receipts test of IRC §448(c), and related-party aggregation rules apply — businesses under common control are combined for this test.

Carryforward Mechanics by Entity Type

How disallowed BIE is tracked and utilized differs by entity:

  • Partnerships: Disallowed BIE is not retained at the partnership level. It is allocated to partners as excess business interest expense (EBIE) on Schedule K-1 (Box 13, Code K). Partners use the EBIE when the partnership later allocates excess taxable income (ETI) back to them. Remaining EBIE upon disposition of the partnership interest is deductible in the sale year.
  • S-Corporations and C-Corporations: Disallowed BIE carries forward at the entity level. The entity deducts the carryforward in a future year when ATI provides sufficient capacity. Shareholders do not track carryforwards individually.

The Real Estate Opt-Out Election

Real property trades or businesses may make an irrevocable election under §163(j)(7) to exclude themselves from the limitation entirely. The cost of the election: the taxpayer must use the Alternative Depreciation System (ADS) rather than MACRS for residential rental property, nonresidential real property, and qualified improvement property — forfeiting bonus depreciation eligibility on those assets. See MACRS for how GDS and ADS depreciation schedules compare.

After the OBBBA EBITDA restoration, many real property businesses that previously found the election beneficial should model the tradeoff fresh: a higher ATI base may allow full interest deductibility without requiring an irrevocable switch to ADS.

Related Terms

  • Adjusted Taxable Income (ATI) — the income measure computed under §163(j) that forms the 30% deductibility base; covers the EBITDA addback restoration and partnership ETI mechanics
  • Section 163(j) Business Interest Limitation: OBBBA Planning Guide — the full CPA planning guide covering ATI modeling, carryforward utilization, the new capitalized interest rule, and entity-specific planning strategies
  • At-Risk Rules — another loss limitation under IRC §465 that applies before passive activity rules and before §163(j) in the loss ordering sequence
  • Passive Activity Loss — IRC §469 restrictions on using passive losses to offset non-passive income; interacts with §163(j) for real estate activities
  • Excess Business Loss — the §461(l) limitation that applies after §163(j); non-corporate taxpayers face a third limitation cap once business losses exceed the annual statutory threshold
  • MACRS — the depreciation system whose D&A amounts flow into the EBITDA-based ATI addback, and the system forfeited (in favor of ADS) by electing real property businesses under §163(j)(7)

How CPAs Use This in Practice

The business interest limitation surfaces in three common planning contexts. Leveraged buyouts and acquisitions: When a client acquires a business using significant debt, CPAs model whether projected EBITDA-based ATI will support full deductibility of the acquisition financing — and build out a carryforward utilization schedule for excess BIE in early years when ATI may be compressed by integration costs. Real estate portfolio decisions: Clients with mixed-use real estate must decide annually whether the §163(j)(7) ADS election is optimal. The OBBBA EBITDA addback shifts the breakeven point — modeling the present-value cost of ADS depreciation against the benefit of uncapped interest deduction is now required before making an irrevocable election. Partnership interest allocations: For clients invested in multiple partnerships, CPAs track EBIE by partnership on Schedule K-1 and coordinate ETI allocations to ensure carryforwards are utilized efficiently across the portfolio.

For a complete walkthrough of §163(j) planning under the OBBBA — including the 2026 capitalized interest rule change and S-Corp vs. partnership carryforward mechanics — see Section 163(j) Business Interest Limitation: OBBBA Planning Guide for CPAs.