Businesses that use debt to finance expansion, equipment, acquisitions, real estate, or working capital need to pay close attention to the federal business interest deduction rules in 2026. Changes to the calculation of adjusted taxable income under Section 163(j) can affect how much business interest a company can deduct in the current year and how much may need to be carried forward.
For growing companies working with professional tax planning services, understanding these rules is particularly important because borrowing decisions can have tax consequences beyond the interest rate on a loan. A financing structure that appears attractive from a cash-flow perspective may produce a different tax result depending on the company’s income, depreciation, interest expense, and business structure.
The 2026 rules make it increasingly important to evaluate business financing decisions alongside tax projections rather than waiting until the tax return is prepared.
What Is The Business Interest Deduction?
Section 163(j) generally limits the amount of business interest expense that certain taxpayers can deduct in a tax year.
Under the general limitation, deductible business interest is generally limited to the sum of business interest income, 30% of adjusted taxable income, and floor plan financing interest. Any business interest expense that is disallowed may generally be carried forward under the applicable rules.
The rule is designed to limit the amount of interest expense that certain businesses can use to reduce taxable income in a particular year.
For businesses with significant borrowing, this can become an important tax-planning issue. A company may have a legitimate interest expense deduction on its books but still be unable to deduct the entire amount immediately for federal income tax purposes.
What Changed For 2026?
One of the most important developments for 2026 involves the definition of adjusted taxable income used in the Section 163(j) calculation.
The One, Big, Beautiful Bill Act restored depreciation, amortization, and depletion to the add-back calculation for adjusted taxable income for tax years beginning after December 31, 2024. This means that, for applicable years, adjusted taxable income is generally calculated without reducing it by deductions for depreciation, amortization, or depletion.
This is significant because adjusted taxable income is used to determine the amount of interest a business may deduct under the 30% limitation.
In practical terms, the change can increase the adjusted taxable income base for businesses with substantial depreciation, amortization, or depletion deductions. A higher adjusted taxable income amount can potentially produce a larger Section 163(j) interest deduction.
Why Depreciation Matters
Depreciation can substantially reduce taxable income for businesses that invest in equipment, machinery, technology, vehicles, and other qualifying assets.
The 2026 rules are especially relevant because qualifying businesses may also have access to 100% bonus depreciation for eligible property acquired after January 19, 2025.
Without the Section 163(j) change, a company with significant depreciation deductions could have a lower adjusted taxable income figure for purposes of the interest limitation. The restoration of depreciation as an add-back changes that calculation.
This does not mean every business will automatically receive a larger interest deduction. The actual result depends on the company’s complete tax profile, including business interest income, interest expense, taxable income, and other applicable rules.
How The Rule Can Affect A Growing Business
Consider a company that borrows heavily to expand its operations.
The company may have substantial interest expense because it financed a new facility, purchased equipment, or acquired another business. At the same time, it may claim significant depreciation deductions associated with those investments.
Under the current 2026 framework, depreciation is generally added back when calculating adjusted taxable income for Section 163(j) purposes. That can increase the amount of adjusted taxable income used in the 30% calculation.
As a result, the company may have greater current-year interest deduction capacity than it would under a calculation that reduced adjusted taxable income for depreciation.
This is particularly relevant for capital-intensive companies where borrowing and depreciation are both significant.
Interest Expense And Debt-Financed Growth
Debt can be an effective way to fund expansion without immediately issuing additional equity, but the tax treatment of interest should be part of the financing analysis.
A business considering a new loan should evaluate more than the interest rate. Management should also consider the expected amount of deductible interest, the timing of the deductions, the company’s projected taxable income, and whether any interest could become subject to Section 163(j).
This is especially important when a company expects to experience rapid growth.
A business might take on substantial debt during an expansion period while taxable income changes significantly from year to year. If interest expense exceeds the amount currently deductible, the resulting carryforward can affect future tax planning.
Carryforwards Can Matter
When business interest is limited under Section 163(j), the disallowed amount is generally carried forward for use in future years, subject to the applicable rules.
This means a limitation does not necessarily mean the business permanently loses the deduction.
However, a carryforward can still create a timing issue. The business may incur the cash cost of paying interest today while receiving the tax deduction later.
That difference between economic cash flow and tax deductibility should be incorporated into financial forecasts.
Which Businesses Need To Pay Particular Attention?
The rules can be particularly important for businesses with substantial debt relative to their operating income.
Real estate businesses, manufacturers, construction companies, transportation businesses, acquisition-focused companies, and rapidly expanding service businesses can all encounter situations where interest expense becomes a meaningful component of their tax calculation.
The impact can also vary significantly depending on the company’s entity structure and the type of activities it conducts.
Not every business is subject to Section 163(j) in the same way. Certain small businesses may qualify for an exemption from the limitation if they meet the applicable gross receipts test and other requirements. The IRS publishes inflation-adjusted amounts for determining whether a taxpayer meets the small-business exception.
Because eligibility depends on specific requirements, businesses should determine whether they are actually subject to the limitation before building their strategy around it.
The Small Business Exception Can Be Important
The small-business exemption can prevent qualifying businesses from being subject to the Section 163(j) limitation.
For tax years beginning in 2026, the inflation-adjusted average annual gross receipts threshold used for the small-business exemption is $32 million.
The test generally uses average annual gross receipts over a specified period and includes aggregation rules that can require businesses under common control to consider the receipts of related entities.
This means a company should not look only at its current year’s revenue.
A business that has grown substantially may cross the applicable threshold and become subject to rules that did not previously affect it. Conversely, a smaller business may remain outside the limitation if it continues to satisfy the requirements.
How 2026 Equipment Investments Can Interact With Interest Deductions
The relationship between depreciation and interest deductions makes capital investment planning particularly relevant in 2026.
Suppose a business uses debt to finance qualifying equipment. The transaction can create both interest expense and depreciation deductions.
Under the updated Section 163(j) calculation, depreciation, amortization, and depletion are generally added back when determining adjusted taxable income for applicable years. At the same time, qualifying equipment may be eligible for 100% bonus depreciation.
This creates an important planning interaction.
The business may receive accelerated depreciation for its equipment while calculating its Section 163(j) interest limitation using an adjusted taxable income figure that adds back depreciation.
That combination can make the tax treatment of debt-financed investments different from what a business owner might expect by looking at taxable income alone.
Businesses Should Not Borrow Solely For A Tax Deduction
Interest is a business expense, but deductibility should never be the primary reason to take on debt.
If a company borrows $1 million and pays interest on that debt, the business does not become financially better simply because some portion of the interest may be deductible.
The loan should support an investment that is expected to generate sufficient economic value.
Tax savings can reduce the after-tax cost of borrowing, but they do not eliminate the principal obligation or the financing expense.
This distinction becomes especially important when interest deductions may be limited or deferred.
Tax Planning Should Begin Before Financing Decisions
Businesses considering significant financing in 2026 should model the tax implications before signing major loan agreements.
A tax projection can help estimate the company’s expected taxable income, interest expense, depreciation deductions, and potential Section 163(j) limitation.
Management can then compare different financing structures and determine whether the expected tax treatment supports the overall business case.
For companies considering acquisitions, the analysis can become more complex because purchase price allocation, debt structure, depreciation, amortization, and the treatment of interest can all interact.
Professional tax advice can be particularly useful when the financing transaction is large enough to materially affect the company’s tax position.
What Growing Companies Should Review In 2026
A business that has increased its borrowing should review whether Section 163(j) applies and whether the company qualifies for an applicable exception.
It should also review projected interest expense, depreciation and amortization, business interest income, and any existing interest carryforwards.
Companies with related entities should consider whether aggregation rules affect the analysis.
The objective is to understand the expected tax treatment before year end rather than discovering an unexpected limitation after the books have closed.
Conclusion
The 2026 business interest deduction rules deserve attention from any growing company that relies heavily on debt. The restoration of depreciation, amortization, and depletion as additions in the adjusted taxable income calculation can materially affect the Section 163(j) limitation, particularly for businesses with significant capital investments.
At the same time, the small-business exception, interest carryforwards, business structure, and financing arrangements can substantially change the result from one company to another.
Business owners should therefore avoid assuming that all interest is automatically deductible or that every company faces the same limitation. A financing decision should be evaluated based on its commercial benefits, cash-flow impact, and expected tax consequences.
For companies planning expansion, acquisitions, equipment purchases, or other debt-financed investments in 2026, incorporating business interest deductions into a broader tax strategy can help management make financing decisions with a clearer understanding of both current and future tax consequences.