Missed Depreciation? How the Form 3115 Catch-Up Works

By Tom, CPA · Updated October 27, 2026

Part of: Rental Property Taxes

TL;DR: If you never claimed depreciation on a rental, you can usually catch up all of it in the current year by filing Form 3115 for an automatic change in accounting method, taking a negative Section 481(a) adjustment. If you only missed one year, amending that return is often the right fix instead.

Educational only, not tax, legal, or investment advice. Examples are illustrations, not predictions. Rules and limits change; verify current figures and talk to a qualified professional about your situation.

Your tenant pays the mortgage; the IRS pays for the roof, eventually, over 27.5 years. Unless you forgot to ask. A surprising number of landlords, especially self-preparers and people who converted a former home into a rental, never claimed depreciation. Some skipped it on purpose because a forum said it "just gets recaptured anyway."

That logic fails for one reason: when you sell, your basis is reduced by depreciation "allowed or allowable," whichever is greater (IRS Publication 946 and Publication 544). Translation: you pay recapture tax on depreciation you never deducted. That is the tax equivalent of paying for a buffet and leaving before eating. The good news is that the tax code has a catch-up mechanism, and it is friendlier than most people expect.

CPA Warning Label: The catch-up deduction is still subject to the passive loss rules. A giant 481(a) adjustment can land on your return and then sit suspended.

Allowed or allowable

"Allowed" is depreciation you actually deducted. "Allowable" is depreciation you were entitled to deduct. When you sell, basis is reduced by the larger of the two. So missed depreciation does not vanish; it becomes a pure loss of a deduction you were owed.

The IRS treats a consistent failure to depreciate an asset as an impermissible method of accounting once the incorrect treatment has appeared on two or more consecutively filed returns. That matters, because the remedy for a method problem is a change in accounting method, not an amended return. If the error only shows up on one return, it is typically not yet a method, and you fix it by amending.

Common ways people end up here: they converted a residence to a rental and did not set up the asset; they depreciated the land along with the building (overstated depreciation, also a problem); they used the wrong recovery period, such as 39 years on a residential building; or they never capitalized a big improvement like a roof.

Automatic change

Form 3115, Application for Change in Accounting Method, is the vehicle. The IRS publishes a list of automatic changes that do not require advance consent or a user fee. Changing from an impermissible to a permissible method of depreciation for property you still own is one of them; the Form 3115 instructions refer to it by its designated change number (commonly DCN 7) and the current revenue procedure listing automatic changes.

Mechanics in plain English:

• Attach the original Form 3115 to your timely filed (including extensions) federal return for the year of change.
• File a signed duplicate copy with the IRS office listed in the instructions, no earlier than the first day of the year of change and no later than the date you file the original with your return.
• Start depreciating correctly in the year of change, as if you had been doing it all along.
• Report the cumulative missed depreciation as a Section 481(a) adjustment.

Yes, the form is long and intimidating. Most of the questions do not apply to a small landlord, but the ones that do must be answered precisely, including the property description, placed-in-service date and the computation.

481(a) adjustment

The Section 481(a) adjustment is the difference, as of the beginning of the year of change, between the depreciation you should have taken under the correct method and what you actually took. If you took too little, the adjustment is negative, which reduces income, and per the Form 3115 instructions a negative adjustment is generally taken entirely in the year of change. A positive adjustment (you took too much) is generally spread over four years.

This is the best part: the negative adjustment captures all prior years, including years closed by the statute of limitations. Amended returns can only reach open years, generally three years back. The method change sweeps up everything.

On a rental, the adjustment is treated as part of the rental activity. That means it is subject to the passive loss rules in Publication 925. If you actively participate and your modified AGI is under $100,000, up to $25,000 of total rental loss can offset other income; above $150,000 the allowance is gone and the loss may be suspended until you have passive income or sell.

When to amend instead

• Only one return is wrong. If you placed the property in service last year and forgot depreciation on that one return, you have not adopted a method yet. Amend that return.
• You want the deduction in a specific prior year. Amending may matter if the prior year had a higher tax rate. The 3115 puts the catch-up in the current year.
• The property has already been sold. The automatic method change generally requires that you still own the property at the beginning of the year of change. For a property sold in a prior year, amending open years is generally the remaining option.

When in doubt, run both versions. The 3115 almost always wins when several years are missed, simply because it recovers closed years.

Example

Illustration: Frugal Fran converted her former home into a rental and placed it in service in January 2020. The depreciable basis of the building (the lower of adjusted basis or fair market value at conversion, excluding land) is $220,000. She never claimed depreciation for 2020 through 2025. In 2026 she files Form 3115.

Her rental otherwise breaks even, so she shows a $55,667 rental loss. Her modified AGI is $85,000 and she actively participates, so $25,000 offsets her pension and other income this year. The remaining $30,667 is a suspended passive loss carried forward. If she had amended instead, she could only have reached open years (as of October 2026, generally 2023 through 2025), losing the 2020 through 2022 deductions permanently. Using the 3115, her adjusted basis now properly reflects the $55,667, and every dollar was deducted somewhere.

Simplified for illustration; actual figures depend on the IRS mid-month tables and the conversion basis rules.

Special cases

Converted residences

When a former home becomes a rental, the depreciable basis is the lower of the adjusted basis or the fair market value on the conversion date, excluding land (Publication 527). People often skip this because no purchase happened in the rental year, so the software never asks. Gather the original closing statement, improvement records and a reasonable estimate of value on the conversion date.

Improvements never capitalized

A roof, HVAC system or kitchen remodel that was expensed or ignored also needs fixing. If it was expensed as a repair in a single year, that is a different problem (an overstated deduction); if it was simply never recorded, it belongs in the 3115 catch-up as its own asset with its own life.

Wrong recovery period

Depreciating a residential rental over 39 years, or using a non-MACRS method, is also an impermissible method fixed with the same automatic change, and the 481(a) adjustment captures the difference.

Vacant periods

Depreciation continues while a property is held out for rent, even if vacant between tenants. Stopping depreciation during a vacancy is another way people end up with "allowable but not allowed" depreciation.

Getting it right

• Gather the facts first: purchase or conversion date, cost, land allocation, improvements and when each was placed in service.
• Compute the correct schedule for every asset, using IRS Publication 946 tables.
• Watch the land. If you depreciated land, the correction is a positive adjustment.
• Keep the computation with your return records. If the IRS asks, the schedule is your proof.
• Check state conformity. Most states follow the federal method change, but some handle adjustments differently.

For households with several properties or prior bonus elections, professional help on the 3115 is often worth the cost; the form rewards precision.