Amending Prior Returns vs. Filing Form 3115: Which Is Better for Missed Depreciation?

When a rental property owner discovers they've been under-depreciating for years, two paths exist: (1) amend each prior year's return to claim the additional depreciation, or (2) file Form 3115 and take all the missed depreciation as a catch-up deduction in the current year. Most of the time, Form 3115 wins. Here's why — and when the calculus changes.

Path 1: Amending Prior Returns

An amended return (Form 1040-X) lets you correct a previously filed return within the statute of limitations — generally 3 years from the original filing date or 2 years from the tax payment date, whichever is later. For depreciation corrections, the IRS also allows amendments within 3 years even if the original error was a failure to claim a deduction.

If you missed $20,000 of depreciation in 2023 and $20,000 in 2024, you could theoretically file two amended returns and get refunds for both years. Sounds appealing — but there are significant drawbacks.

• You can only go back 3 years. Any years outside the statute of limitations are locked out.
• Each amended return costs money. CPA fees for 1040-X preparation add up quickly, and each year is a separate filing.
• Amended returns get more scrutiny. They sit in a separate IRS processing queue and are more likely to trigger correspondence or examination.
• Refunds take time. The IRS routinely takes 6–12 months to process amended returns.
• You cannot amend a year where bonus depreciation applied differently. If the 2022 rate was 80% but you're claiming the 2025 rate of 100%, that's an error — each year must use its applicable rate.

Path 2: Form 3115 (Recommended for Most)

Form 3115 treats the switch from straight-line to MACRS accelerated depreciation as a change in accounting method. The catch-up amount — everything you should have deducted from day one to the present — flows into your current-year return as a Section 481(a) adjustment. You get all the missed deductions at once, in one filing.

• No statute of limitations. You can catch up depreciation from any prior year, even beyond the 3-year amendment window.
• One filing. Everything is handled on your current return — one Form 3115, one additional attachment, no multiple amended returns.
• Faster cash benefit. The deduction reduces your current-year tax liability or generates a refund on your current-year return, which processes normally.
• Lower audit profile. Automatic consent method changes are routine — the IRS processes thousands of these annually.
• No interest. Unlike an amended return (where you may owe interest on underpaid taxes in other years), Form 3115 has no interest component for a catch-up.

When Amending Might Be Better

There are narrow situations where amending prior years makes more sense:

• You have NOL carrybacks available in a prior year that you want to activate (high-income year in the past that Form 3115 can't reach)
• The property was sold in a prior year and the basis correction affects a prior-year gain calculation
• You're correcting an error (like accidentally depreciating land) rather than changing a method — errors must be corrected by amendment, not Form 3115
• A prior-year return has already been audited and the IRS adjusted depreciation upward — consult counsel before filing a competing Form 3115

The Verdict

For the vast majority of STR investors who simply used straight-line depreciation and never did a cost segregation study, Form 3115 is the right tool. It captures more years of missed depreciation than amendments can (no 3-year limit), costs less in CPA time, and gets you the benefit faster.