Your Mortgage Interest Deduction Isn’t Guaranteed. Here’s What §163(j) Means for Real Estate Investors

You bought a rental property in Florida, took out a mortgage, and assumed you’d deduct every dollar of interest on your tax return. Most investors do. But §163(j) of the Internal Revenue Code says: not so fast.

Since 2018, this provision has capped how much business interest expense you can deduct each year. The cap is 30% of your adjusted taxable income (ATI), plus any business interest income you earned. If your interest expense exceeds that number, the excess gets carried forward. Not lost, but not usable right now either.

For real estate investors carrying significant mortgage debt, this matters. And the rules changed again in 2025 when Congress passed the One Big Beautiful Bill Act (OBBBA). Whether the change helps you or hurts you depends on elections you’ve already made (or haven’t).

This article breaks down the §163(j) limitation, explains the RPTB election (and why it might now be a trap), and covers what the OBBBA changed for tax years starting in 2025 and beyond.

How the §163(j) Limitation Actually Works

The Basic Formula

Your deductible business interest expense for any tax year is limited to:

• Business interest income (interest you earn from business activities)
• Plus 30% of adjusted taxable income (ATI)
• Plus floor plan financing interest (irrelevant for most real estate investors)

Any interest expense above that amount gets carried forward indefinitely. You don’t lose it, but you can’t use it this year.

What Goes Into ATI

This is where things got complicated. ATI starts with taxable income and adds back certain items. The original TCJA formula (2018–2021) added back depreciation, amortization, and depletion, making ATI an EBITDA-like number. Higher ATI meant a higher 30% cap, which meant more interest you could deduct.

Then from 2022 through 2024, Congress stripped the depreciation add-back from ATI. Your ATI became an EBIT-based number. If you had large depreciation deductions (say from a cost segregation study or bonus depreciation), your ATI dropped, your 30% cap dropped, and suddenly a big chunk of your mortgage interest got disallowed.

Capital-heavy businesses like real estate got squeezed the hardest. The more depreciation you claimed, the less interest you could deduct. Depreciation was cannibalizing interest deductibility.

A Quick Example

Say you own a vacation rental that generates $200,000 in rental income and you have $120,000 in operating expenses (not counting depreciation or interest). You claimed $60,000 in depreciation and paid $50,000 in mortgage interest.

Under 2022–2024 rules (EBIT-based ATI):

• Taxable income before interest: $200,000 − $120,000 − $60,000 = $20,000
• ATI = $20,000 (no depreciation add-back)
• 30% of ATI = $6,000
• Deductible interest = $6,000. The other $44,000 carries forward.

Under 2025+ rules (EBITDA-based ATI, post-OBBBA):

• Taxable income before interest: $20,000
• ATI = $20,000 + $60,000 depreciation add-back = $80,000
• 30% of ATI = $24,000
• Deductible interest = $24,000. Only $26,000 carries forward.

That’s $18,000 more in deductible interest just from the ATI calculation change. For investors with aggressive cost segregation, the swing can be even larger.

The OBBBA Fix: EBITDA Is Back (Permanently)

The One Big Beautiful Bill Act, signed into law in 2025, made two changes that matter for debt-heavy real estate investors:

1. ATI is EBITDA-based again. Starting with tax years after December 31, 2024, depreciation, amortization, and depletion are added back into ATI. This is permanent. No sunset, no phase-out. The 2022–2024 squeeze is over.

2. 100% bonus depreciation is permanent. The TCJA had bonus depreciation phasing down (80% in 2023, 60% in 2024, 40% in 2025, scheduled to hit 0% by 2027). OBBBA restored 100% bonus depreciation for qualified property acquired and placed in service after January 19, 2025.

These two changes work together. You can now accelerate depreciation through cost segregation AND deduct substantial mortgage interest in the same year. From 2022 to 2024, picking one often meant sacrificing the other. That trade-off is gone.

The RPTB Election: What It Is and Why It Might Be a Trap Now

What the Election Does

A qualifying real property trade or business (RPTB) can make a special election under §163(j)(7)(B), called the ERPTOB election, to skip the interest limitation entirely. No 30% cap. All your business interest expense is deductible, period.

Sounds great. But there’s a cost.

The Trade-Off

Making the ERPTOB election forces you to use the Alternative Depreciation System (ADS) for certain property:

• Residential rental property: 30-year recovery instead of 27.5 years
• Nonresidential real property: 40-year recovery instead of 39 years
• Qualified improvement property (QIP): 20-year recovery instead of 15 years

More importantly: ADS property does not qualify for bonus depreciation under §168(k). So if you made the ERPTOB election, your QIP (things like interior renovations, HVAC upgrades, and other improvements) couldn’t be expensed in year one. You had to spread those deductions over 20 years.

The election is also irrevocable. Once you made it, you were locked in.

Why the Math Changed

Before the OBBBA, the election made sense for many debt-heavy real estate portfolios. The §163(j) limitation was biting hard, especially with EBIT-based ATI from 2022 to 2024. Giving up some depreciation speed to unlock full interest deduction was a reasonable trade.

Now? With EBITDA-based ATI restored and 100% bonus depreciation permanent, the calculation flips:

• Many investors can deduct most or all of their interest expense without the ERPTOB election (because higher ATI means a higher 30% cap)
• Making the election now costs you 100% bonus depreciation on QIP — a much steeper price than when bonus depreciation was already phasing down
• The “benefit” side of the election shrinks while the “cost” side grows

For most rental real estate investors filing in 2025 and beyond, the ERPTOB election went from “probably worth it” to “probably not.”

Rev. Proc. 2026-17: The IRS Lets You Undo the Election

The IRS recognized the problem. In March 2026, the IRS issued Revenue Procedure 2026-17, allowing taxpayers who made the ERPTOB election for tax years beginning in 2022, 2023, or 2024 to withdraw it.

How It Works

• File an amended return (or amended Form 1065 / AAR for partnerships) for the year the election was originally made
• The withdrawal treats you as if the election was never made
• Depreciation gets recalculated under non-ADS rules
• You can simultaneously make a late §168(k)(7) election to opt out of bonus depreciation for specific property classes, giving you control over how much depreciation shifts

The Deadline

The deadline to withdraw is October 15, 2026, or potentially earlier depending on when prior returns were filed. If you’re sitting on an ERPTOB election from 2022–2024, this is a time-sensitive opportunity.

Partnership Considerations

If the election was made by a partnership, withdrawing affects partner capital accounts. The effect of the withdrawal must be reflected in capital accounts to maintain substantial economic effect under the regulations. This isn’t a paperwork detail. It can affect allocations and distributions.

Who Benefits Most From These Changes

NRA Investors With Florida Vacation Rentals

If you’re a nonresident alien owning short-term rental property in Florida through a US entity (LLC taxed as partnership or corporation), you likely carry mortgage debt and have done (or should do) a cost segregation study. The OBBBA changes directly affect your bottom line:

• Higher ATI means more interest is deductible without any special election
• 100% bonus depreciation on qualified property placed in service after January 19, 2025, accelerates deductions
• If you made the ERPTOB election in 2022–2024, you should run the numbers on withdrawing it

Investors Who Did Cost Segregation Studies

Cost segregation reclassifies building components into shorter recovery periods (5, 7, or 15 years instead of 27.5 or 39). With 100% bonus depreciation back, those reclassified components can be fully expensed in year one. And because ATI now adds back that depreciation, claiming it doesn’t torpedo your interest deduction like it did from 2022 to 2024.

Debt-Heavy Portfolios

If your interest expense is significant relative to your rental income, run a comparison: what’s your §163(j) limitation with EBITDA-based ATI versus the benefit of the ERPTOB election? For many portfolios, the limitation is no longer binding, and the election’s depreciation penalty isn’t worth paying.

Common Mistakes to Avoid

• Assuming all mortgage interest is automatically deductible. §163(j) applies to business interest expense. If you don’t run the ATI calculation, you might miss disallowed interest that should carry forward.
• Making the ERPTOB election without running post-OBBBA numbers. The election is still irrevocable from now on. Before electing for 2025+, model both scenarios with your actual depreciation and interest figures.
• Missing the October 15, 2026 withdrawal deadline. If you elected ERPTOB in 2022–2024, Rev. Proc. 2026-17 gives you a narrow window. Don’t sit on it.
• Ignoring partnership capital account impacts. Withdrawing an ERPTOB election in a partnership changes depreciation retroactively. Capital accounts and allocations need to be restated.
• Forgetting state conformity. Not all states follow federal bonus depreciation or §163(j) rules. Your federal deduction might not carry over to your state return.

The Bottom Line

• §163(j) caps business interest deductions at 30% of ATI — and ATI is now EBITDA-based again (permanently) thanks to the OBBBA
• The ERPTOB election eliminates the interest cap but forces ADS depreciation and kills bonus depreciation on affected assets
• With 100% bonus depreciation restored and higher ATI, the ERPTOB election is a worse deal for most real estate investors than it was from 2022–2024
• Rev. Proc. 2026-17 lets you withdraw ERPTOB elections made in 2022–2024 — deadline is October 15, 2026
• NRA investors with financed Florida rentals should model both scenarios before their next filing

How Celeraxiom Can Help

At Celeraxiom, we work with nonresident alien investors and foreign-owned LLCs that hold rental property in Florida. We model the §163(j) limitation against the ERPTOB election for every client — factoring in cost segregation, bonus depreciation, and the OBBBA changes. If you made the election and want to evaluate pulling it back under Rev. Proc. 2026-17, we can run the numbers and handle the amended filings before the October 2026 deadline.

Frequently Asked Questions

Does §163(j) apply to my rental property if I’m not a US citizen?

Yes. If you own rental property in the US and the rental activity is treated as a trade or business (or you’re filing through a partnership or corporation that has business interest expense), §163(j) applies regardless of your citizenship or residency status. NRA investors filing Form 1040-NR or through a US entity are subject to the same rules.

Can I still make the ERPTOB election for tax year 2025?

You can, but you should think carefully before doing so. With EBITDA-based ATI restored and 100% bonus depreciation permanent, the benefit of unlimited interest deduction may not outweigh the cost of losing bonus depreciation and being locked into ADS recovery periods. Run the numbers with your specific income, depreciation, and interest figures before deciding.

What happens to my disallowed interest from prior years?

Disallowed business interest expense under §163(j) carries forward indefinitely. It can be deducted in future years when your ATI is high enough to support the deduction. With the OBBBA restoring the EBITDA-based ATI calculation, some of your carried-forward interest from 2022–2024 may become deductible starting in your 2025 tax year.

What is a cost segregation study and how does it relate to §163(j)?

A cost segregation study reclassifies components of a building (fixtures, land improvements, certain equipment) from the building’s 27.5 or 39-year life into shorter 5, 7, or 15-year categories. Those reclassified assets qualify for bonus depreciation. Under the OBBBA, this accelerated depreciation increases ATI (because depreciation is added back), which increases your §163(j) interest deduction cap. Before the OBBBA, the opposite was true — more depreciation meant less interest you could deduct.

Is the deadline to withdraw the ERPTOB election really October 15, 2026?

That’s the latest possible date under Rev. Proc. 2026-17, but the actual deadline could be earlier depending on when your original or amended returns were filed. Consult your tax advisor to determine your specific deadline, and don’t wait until the last minute — amended returns and AARs take time to prepare.