Forgot to take depreciation on your rental? Here is how to fix it

It usually surfaces one of two ways. A new CPA looks at last year's return and asks for the depreciation schedule, and there is no schedule. Or you are working through Schedule E yourself, hit line 18, and realize it has been blank since you bought the place. Either way the reaction is the same: a quiet panic about how many thousands of dollars in deductions you skipped, and whether fixing it means amending a stack of old returns.

Here is the short version. Depreciation on a rental is not optional in any way that matters, the IRS treats it as taken whether you claimed it or not, and the usual fix is a single form filed with the current year's return, not a pile of amendments. The missed deductions typically come back to you in one tax year. But the right path depends on exactly how many returns you filed without it, so the first job is to count.

The allowed or allowable rule: why skipping never works

Most deductions are use-it-or-lose-it. Depreciation is worse: lose it and you still pay for it. The tax code requires you to reduce your cost basis by the depreciation allowed or allowable, whichever is greater. Allowed means what you actually claimed. Allowable means what you could have claimed under the rules in IRS Publication 946. If line 18 has read zero for six years, your basis still dropped by six years of deductions you never used.

That basis reduction is where it bites. When you sell, the depreciation portion of your gain is taxed as unrecaptured section 1250 gain at rates up to 25%, and recapture is computed on the allowable number, not the claimed one. A landlord who never depreciated sells the property and pays recapture as if every year had been deducted. Of everything that can go wrong in rental property taxes, this is the only mistake that taxes you on money you never saved. The schedule runs whether you ride it or not.

What the miss is worth, in real numbers

Say you bought a single-family rental in January 2020 for $275,000 and the county assessor's card puts the land at $55,000. Your building basis is $220,000, and residential rental property depreciates straight-line over 27.5 years.

Annual depreciation = building basis ÷ 27.5 = $220,000 ÷ 27.5 = $8,000 per year.

The first year is prorated under the mid-month convention, so the 2020 deduction is $7,667 rather than $8,000. Through the 2025 return that is $7,667 plus five full years at $8,000: $47,667 of allowable depreciation. If you claimed none of it, three things are true at once:

• Your basis already dropped. The property's adjusted basis fell by $47,667 whether or not your returns show a single dollar of it.
• Recapture is already loaded. Sell tomorrow and up to 25% of that $47,667, as much as $11,917, comes due as unrecaptured section 1250 gain on deductions you never took.
• The catch-up is real money. Deduct the full $47,667 in one return at a 24% marginal rate and it is worth about $11,440 in federal tax, before any state effect.

Run your own building basis through the depreciation calculator before you call anyone. Knowing whether your miss is $4,000 or $47,000 changes the urgency of the conversation.

The decision tree: amend, or Form 3115

The fix turns on one count: how many returns you filed with the wrong depreciation treatment. Not how many years you have owned the property, how many returns.

• One return. If the error sits on a single filed return, say you bought the place last year and missed depreciation on that first Schedule E, you have not adopted an accounting method. The fix is an amended return for that year, generally available for about three years after the original filing.
• Two or more consecutive returns. Once the same wrong treatment, including claiming zero, appears on two consecutively filed returns, the IRS considers it your accounting method. You can no longer amend your way out. The fix is Form 3115, Application for Change in Accounting Method, filed with the current year's return.

The second branch surprises people, then turns out to be the better one. Amending caps you at the lookback window, roughly three years, while the method change pulls every missed year into the current return. A landlord who never depreciated for ten years cannot amend ten returns, but Form 3115 recovers all ten years at once. Edge cases exist (a one-off math slip is not a method, for instance), which is part of why the branch you are on is a question for your CPA, not a forum thread.

How the Form 3115 catch-up works

Form 3115 sounds like a fight with the IRS. For this specific fix it is closer to paperwork with a known outcome. Correcting depreciation from an impermissible method, including no depreciation at all, to the proper method is an automatic change under Rev. Proc. 2015-13, listed as designated change number 7 (DCN 7) on the IRS's automatic change list. Automatic means no advance permission and no user fee: the form is attached to a timely filed return, a copy goes to the IRS separately, and consent is granted by the procedure itself.

The engine inside the form is the section 481(a) adjustment: the difference between what you claimed and what was allowable. When the adjustment favors you, the entire amount is deducted in the year of change. Six missed years, like the $47,667 above, land on one Schedule E in one tax year, with no reopened returns built into the process.

Two caveats belong in the same breath. First, a deduction that large often turns the year into a paper loss, and rental losses are passive, so the passive activity rules decide how much you use now and how much carries forward. Second, the Form 3115 instructions want your original basis, the land split, the in-service date, and a year-by-year schedule of claimed versus allowable amounts. That is the mechanism, not an invitation to file it solo. A depreciation method change is one of the few filings where a few hundred dollars of CPA time is cheap insurance on a five-figure deduction, and your CPA can often file it as late as the year you sell, though the mechanics shift at sale.

What to bring to the meeting

The Form 3115 conversation goes fast when you arrive with the file already built:

• The closing statement from purchase, which fixes your original cost basis and the closing costs that get capitalized into it.
• A defensible land and building split, usually the county assessor's card showing land versus improvements for your purchase year.
• The in-service date, the day the property was ready and available to rent, with the first listing or lease as evidence.
• Every filed Schedule E since purchase, so the claimed-versus-allowable schedule can be built year by year.
• A list of improvements with dates and costs, since a roof or HVAC replacement carries its own depreciation schedule and may have its own missed years.

The same documents feed the rest of your filing, so fold this into your year-end tax prep rather than treating it as a separate scramble. An hour of assembly on your side saves several hundred dollars of CPA archaeology.

Make the schedule impossible to forget

Depreciation gets missed for a mundane reason: it is the one large deduction with no transaction attached. Rent lands in your bank account, repairs produce receipts, but depreciation is a calculated figure that exists only if something calculates it. In a spreadsheet, that something is a cell you built three tabs deep in year one and never looked at again. I self-manage my own small portfolio from two time zones away, and I built rents.ai because spreadsheets kept dropping exactly this kind of silent number: it computes line 18 automatically, straight-line MACRS over 27.5 years with the mid-month first-year proration, from the basis, land value, and in-service date you enter. What it will not do is recover years you already missed or file anything for you. The Form 3115 fix belongs to your CPA, and the app's Schedule E rollup is an estimate to hand them, not tax advice.

However you keep the schedule, keep it somewhere that runs without your memory. A deduction that repeats for 27.5 years should not depend on you remembering it 27 times.