How to Correct Prior Year Depreciation Errors With Form 3115

To correct prior year depreciation errors, you generally file IRS Form 3115, Application for Change in Accounting Method, and take a single Section 481(a) adjustment in the current year rather than amending each old return. An amended return only works when the mistake sits in one recent, still-open tax year. Once the same wrong treatment has appeared on two or more consecutive returns, the IRS treats it as an accounting method, and Form 3115 becomes the required fix.¹

Why the Error Can’t Just Sit There

Section 1016(a)(2) reduces your basis in a depreciable asset by the greater of the depreciation you actually claimed or the depreciation you were entitled to claim.² This is the “allowed or allowable” rule, and it is the reason ignoring a depreciation mistake costs real money.

If you forgot to depreciate an asset for several years and then sell it, the IRS calculates your gain as though you had taken every deduction you were entitled to. You pay tax on a larger gain without ever having received the deductions that reduced it. The deductions themselves are gone for closed years, but the basis reduction stays. Form 3115 exists to prevent that outcome by letting you recapture missed deductions in a single current-year adjustment.

Amended Return or Form 3115

If the error appears on only one recent return and the filing window is still open, an amended return is the right tool. You generally have three years from the date you filed the original return, or two years from the date you paid the tax, whichever is later, to claim a refund through Form 1040-X or its entity equivalent.³

Once the same impermissible treatment has been used on two or more consecutively filed returns, that treatment is your accounting method. Correcting it is a change in accounting method, and the IRS routes those through Form 3115.⁴ The practical payoff is that Form 3115 reaches into closed years. Even if the statute of limitations has long expired on the original returns, the Section 481(a) adjustment captures the cumulative effect of every prior year’s error and corrects it in the current year. You do not amend a stack of old returns.

Records You Need Before You Start

Most corrections stall here. If you cannot reconstruct what you actually claimed versus what you should have claimed, the math will not work. For each affected asset, pull together:

Original cost or unadjusted basis, including capitalized costs like sales tax, delivery, and installation.
Date placed in service, which controls when the recovery period starts and which first-year convention applies.
Asset class and MACRS recovery period. Computers and peripherals fall under a five-year period; office furniture, seven. Full classification tables are in Publication 946.⁵
Depreciation method that should have applied: 200% declining balance, 150% declining balance, or straight-line.
Depreciation actually claimed on each prior-year return.
Any Section 179 expense or bonus depreciation taken in the placed-in-service year, since either reduces the depreciable basis before MACRS begins.

Dig out the old returns and depreciation schedules before you touch a form.

Calculating the Section 481(a) Adjustment

The Section 481(a) adjustment is the single number that captures the entire cumulative error. It equals the total depreciation that should have been claimed through the end of the year before the year of change, minus the total depreciation actually claimed over the same period.⁶

A simple example: you bought equipment for $50,000 in 2020 with a seven-year MACRS recovery period, but you used a ten-year period on your returns. By the beginning of 2026 you should have claimed roughly $43,500 under the correct schedule. You actually claimed only $35,000. Your Section 481(a) adjustment is negative $8,500, representing deductions you were entitled to but never took.

Getting the convention right matters as much as the recovery period. Most personal property uses the half-year convention, treating the asset as placed in service at the midpoint of the first year. If more than 40% of the year’s depreciable property was placed in service in the last quarter, the mid-quarter convention applies instead. The wrong convention throws off every year in the calculation.

Negative Adjustments

A negative adjustment means you under-depreciated. The correction produces a favorable deduction, and the IRS lets you take the entire negative amount in the year of change. For someone who forgot to depreciate an asset entirely, this can be a substantial one-time write-off.

Positive Adjustments

A positive adjustment means you over-depreciated and now owe additional tax. When the adjustment is positive, the IRS generally requires you to spread the income inclusion evenly over four tax years, starting with the year of change. That cushions the impact instead of forcing the entire increase into a single year.

Filing Form 3115 Under Automatic Consent

Most depreciation corrections qualify for the automatic consent procedure. You do not need advance permission from the IRS and you do not pay a user fee. You file the form and consent is presumed unless the IRS later says otherwise.⁷

To use it, you need to:

Enter the Designated Change Number (DCN) that matches your type of depreciation error. Depreciation and amortization changes are listed under Section 6 of Revenue Procedure 2025-23. Common DCN situations cover the wrong recovery period, the wrong depreciation method, failure to claim any depreciation, and the wrong convention.⁸
Confirm the asset or depreciation issue is not currently under IRS examination.
Meet the scope representations on the form, including the certification that the change does not involve a partnership item under the centralized audit regime.
Check the box designating the filing as an automatic change.
Attach a statement describing the asset, the incorrect method, the correct method, and the authority for the change, citing the specific Code sections and the governing revenue procedure.

Qualified small taxpayers may be eligible for a reduced filing requirement on certain DCNs, completing only specified lines and schedules rather than the entire form.⁷ Check whether you qualify before filling out all ten pages.

The Dual Filing Requirement

Form 3115 has a filing quirk that costs people their automatic consent: you have to submit two copies.

Copy one is attached to your timely filed federal income tax return for the year of change. That is the return where the Section 481(a) adjustment lands in your taxable income. If you have an extension, the form is due by the extended deadline.⁷

Copy two goes separately to the IRS National Office in Ogden, Utah, postmarked no later than the date you file the return. The address is Internal Revenue Service, Ogden, UT 84201, Attn: CC:ITA. Keep your certified mail receipt. The IRS does not send a confirmation letter for automatic changes, so that receipt is your only proof of compliance.

When Automatic Consent Isn’t Available

If your situation falls outside the scope limitations, you file Form 3115 as a non-automatic change. That is a different process: you file before the end of the tax year in which the change is to take effect, you pay a user fee, and the IRS must grant written permission before you can implement the change.

The most common disqualifier is that the depreciation issue is already under examination. Filing for a year in which you are under audit, or failing to meet the specific eligibility conditions listed in the revenue procedure for your DCN, will also push you to the non-automatic track. If you are unsure which track applies, the cost of a CPA familiar with Form 3115 is usually well below the cost of botching the filing.

Bonus Depreciation and Section 179 Wrinkles

If the error involves an asset that qualified for bonus depreciation or a Section 179 expense election, the correction gets more layered. Both reduce the depreciable basis before regular MACRS begins, so a first-year miss cascades through every subsequent year.

For 2026, the One Big Beautiful Bill Act restored 100% first-year bonus depreciation for eligible business property acquired after January 19, 2025. If you placed qualifying property in service during the prior phase-down period (2023 through early 2025) and used the wrong reduced bonus percentage, your Section 481(a) adjustment has to account for the bonus depreciation shortfall along with the cascading MACRS effect.

Section 179 has annual dollar limits and taxable income restrictions that change each year. If you elected Section 179 in a prior year, verify the limit that applied in the placed-in-service year. An incorrect Section 179 amount ripples through every subsequent year of MACRS on the remaining basis, and the Section 481(a) calculation has to follow it through.

1
Internal Revenue Service. Revenue Procedure 2004-11
2
Office of the Law Revision Counsel. 26 U.S. Code 1016 – Adjustments to Basis
3
Internal Revenue Service. File an Amended Return
4
Internal Revenue Service. About Form 3115, Application for Change in Accounting Method
5
Internal Revenue Service. Publication 946 How To Depreciate Property
6
Internal Revenue Service. IRC 481(a) Adjustments for IRC 263A Accounting Method Changes
7
Internal Revenue Service. Instructions for Form 3115 – Application for Change in Accounting Method
8
Internal Revenue Service. Revenue Procedure 2025-23 – List of Automatic Changes