Form 3115 and accounting method changes, briefly

An accounting method is any practice that determines when an item of income or deduction is reported — not whether. Cash versus accrual is a method; so is a depreciation recovery period, the treatment of an expense as capital or deductible, and inventory costing. Because a method affects only timing, changing one without supervision would let taxpayers duplicate or vanish deductions at the seam between old and new. Section 446(e) therefore requires the Commissioner's consent to change, obtained on Form 3115, and Section 481(a) supplies the arithmetic that closes the seam.

Automatic versus advance consent

Consent comes in two flavors. Automatic consent covers the changes the IRS has pre-approved in its annually updated List of Automatic Changes (the successor guidance to Rev. Proc. 2015-13's procedural framework). The taxpayer attaches Form 3115 to the timely filed (including extended) return for the year of change and mails a duplicate to Ogden. No user fee, no waiting. Depreciation changes — including adopting the results of a cost segregation study on property placed in service in a prior year — are the classic automatic change (DCN 7), as were the transition methods for Section 174 capitalization in 2022 and the return to Section 174A expensing after the OBBBA.

Advance consent covers everything else. The Form 3115 must be filed during the year of change, a substantial user fee applies, and the IRS National Office reviews and may negotiate terms. Advance consent is the exception in ordinary practice; if a proposed change is not on the automatic list, ask why before proceeding.

The Section 481(a) adjustment

The adjustment answers one question: if the new method had always applied, how would cumulative taxable income differ? A building owner who should have been depreciating $2 million of components over 5 and 15 years, but used 39-year straight line for six years, has under-deducted — say by $700,000. That $700,000 is a negative (taxpayer-favorable) 481(a) adjustment, deducted in full in the year of change. No amended returns, no reopening closed years; the catch-up lands on one return. A positive adjustment — the taxpayer deducted too much, too soon — is generally spread over four tax years, softening the hit.

This mechanism is why a method change is usually preferable to amending returns even when amendment is technically possible: the 481(a) adjustment reaches years already closed by the statute of limitations, in either direction.

Audit protection

The quiet prize of a properly filed change is audit protection: with limited exceptions, the IRS will not require a change for the same item for years before the year of change. A taxpayer who has been using an impermissible method and voluntarily files a 3115 generally locks the exposure into the 481(a) spread rather than facing exam adjustments (with penalties and interest) for open prior years. Protection is not absolute — it is unavailable for an item already under examination when the change is filed, subject to eligibility windows, and can be lost for changes made without the required procedures.

Method changes are plumbing, not strategy. But nearly every specialty tax engagement on prior-year property flows through this pipe, and the taxpayers who understand the 481(a) catch-up and the audit-protection rules capture benefits their neighbors amend for — or forfeit.