If the IRS is going to treat you as if you depreciated the property, you might as well get paid for it.
If you own a rental property and you haven't been claiming depreciation — or you've been claiming too little — you're leaving one of the largest deductions in the tax code on the table. And here's the part that stings: the IRS may tax you as if you claimed it anyway. The good news is that you almost never have to amend a stack of old returns to fix this. One form, filed with a single year's return, can recover every dollar of depreciation you missed since the day you put the property in service. Here's exactly how it works.
The deduction you're required to take — whether you claim it or not
Residential rental buildings depreciate over 27.5 years, straight-line (§167, §168) — the building only; land never depreciates. That's roughly 3.6% of your building basis coming back to you as a deduction every year you own it.
The trap most investors never hear about lives in §1016(a)(2): your basis is reduced by the depreciation “allowed or allowable.” In plain English — when you sell, the IRS computes your gain as if you had taken depreciation every year, even if you never did. Skip it, and you pay tax on a deduction you never received. Depreciation isn't optional money you can leave for later. It's money you simply lose by not claiming it.
Why you can't just amend your old returns
The instinct is to amend the last few years and move on. Two problems. First, you can generally only amend within the statute of limitations — about three years (§6511) — so everything older is closed. Second, and more important: once you've used the wrong depreciation method for two or more consecutive years, the IRS no longer treats it as a simple error. It's now an “accounting method” (Reg. §1.446-1(e)(2)(ii)(d)), and changing an accounting method has its own process — one that happens to be far better than amending.
(Only missed a single year? Then it isn't a method yet — just amend that one return.)
The fix: Form 3115 and the §481(a) catch-up
You file Form 3115, Application for Change in Accounting Method, under the automatic-consent procedures (Rev. Proc. 2015-13) as a change “from an impermissible to a permissible method of accounting for depreciation” — designated change number DCN 7 on the IRS's current List of Automatic Changes. No advance IRS permission required.
The engine that makes this work is the §481(a) adjustment. It sweeps up the entire difference between what you did claim and what you should have claimed — all the way back to the placed-in-service date, not just the open years. And because catching up depreciation is a taxpayer-favorable (negative) §481(a) adjustment, you deduct the whole thing in the year of change. No four-year spread, no amended returns. One filing, one large deduction.
A quick example
Say you bought a residential rental in 2016 for $300,000, with $240,000 allocated to the building. Straight-line over 27.5 years is about $8,727 a year. If you never claimed a dollar of it and you file Form 3115 with your 2025 return, the §481(a) adjustment recaptures roughly nine years of missed depreciation — on the order of $78,000 — as a single deduction on that one return, and you start taking the ~$8,727 annually going forward. Your numbers will differ; the mechanism doesn't.
Where cost segregation pours fuel on the fire
A cost-segregation study breaks the property into components — appliances, flooring, fixtures, land improvements — that depreciate over 5, 7, or 15 years instead of 27.5. Run on a property you've already owned for years, it's a “look-back” study, and the extra depreciation flows through the same Form 3115 §481(a) catch-up.
Under the One Big Beautiful Bill Act (OBBBA, 2025), 100% bonus depreciation (§168(k)) is back — and this time permanent — for qualifying property acquired after 19 January 2025. The building itself (27.5-year property) never qualifies for bonus, but the short-life components a cost-seg study carves out can. That's why pairing a look-back cost seg with today's bonus rules can be powerful. (Property acquired earlier follows the bonus rate in effect for its year.)
The catches — read these before you celebrate
- Passive activity loss rules (§469). Rental losses are generally passive. A large one-year deduction can exceed your passive income and get suspended — you don't lose it, but you may not use all of it this year unless you have passive income, qualify as a real estate professional, or dispose of the property in full.
- Recapture at sale (§1250 / unrecaptured §1250 gain). Depreciation you take — or are treated as taking — is recaptured when you sell, taxed at up to 25% (§1(h)). This is rate-and-timing arbitrage, not free money. But taking ordinary-rate deductions now against a capped 25% rate later is usually a win — and remember, because of “allowed or allowable,” you face the recapture whether or not you ever claimed the deduction. So claim it.
- Mechanics matter. Form 3115 is filed in duplicate — one copy with your timely-filed return, a second with the IRS — and the §481(a) computation has to be right. This is not a DIY form.
Current-law check (as of August 2026)
- Bonus depreciation: 100% and permanent under OBBBA for qualifying property acquired after 1/19/2025 (§168(k)).
- Missed-depreciation change: DCN 7 on the IRS's annually updated List of Automatic Changes (most recently Rev. Proc. 2024-23) under the procedures of Rev. Proc. 2015-13 — confirm the current year's list before filing.
- Tax law changes. Verify before acting.
Think you've been under-depreciating a property?
Grab the free guide: Download The Real-Estate Investor's Tax Playbook — the deductions most investors miss, in plain English.
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This article is general information about U.S. federal income tax, not tax advice for your specific situation. The right answer depends on facts not shown here — how your basis was allocated, your passive-income picture under §469, and whether returns have already been filed taking a position. Run any Form 3115 catch-up by a CPA who can review your documents before you file.
This post is general information about federal and state tax rules, not advice about your situation. Rules change. Check the date above before you rely on anything here, and talk to us about your own facts.