Count the returns first. If you have depreciated the property the same wrong way on 2 or more consecutive returns, Reg. 1.446-1(e)(2)(ii)(d) says you have adopted an accounting method, and a method can only be changed with IRS consent under IRC section 446(e), which means Form 3115, not an amendment. If only one return has been filed since the property was placed in service, no method exists yet; that is an error, and errors are corrected by amending or superseding the return.
Why Form 3115 usually wins anyway
Even when amendment is theoretically available, the method change path has structural advantages:
- No look-back limit. Amended refund claims die at the statute in IRC section 6511, generally 3 years from filing. A section 481(a) adjustment reaches all the way to the placed-in-service date regardless of age.
- One filing. All missed depreciation from every year lands as a single deduction in the current year under Rev. Proc. 2015-13, instead of amending multiple years.
- Automatic consent. The impermissible-to-permissible depreciation change is automatic (designated change number 7), with no user fee, filed with your regular return per the Form 3115 instructions.
When amending is the right call
- The property went into service last year and you have filed only that one return. There is no method to change, so an amended return, or a superseding return if the extended deadline has not passed, is the correct fix.
- You specifically need the deduction in that earlier year, for example to offset an unusually high-income year still open under section 6511, and only one return has been filed.
Worked example
Two investors commission studies in 2026. Investor A bought an $800,000 duplex in mid-2021 ($640,000 depreciable basis) and has filed returns for 2021 through 2025. The study reclassifies 25%, or $160,000. The 27.5-year schedule claimed about $26,000 on that slice; with 100% bonus under IRC section 168(k) in 2021, the correct figure was $160,000. Investor A must file Form 3115 and deducts the roughly $134,000 section 481(a) catch-up on the 2026 return. Investor B bought in June 2025 and filed one 2025 return in February 2026. Investor B simply amends 2025 to apply the study directly, including bonus at the rate the 2025 acquisition date supports.
Caveats
An amendment reopens the amended year to examination adjustments on everything in it; a Form 3115 does not reopen prior years. Neither path helps after the property is sold, and either way the deduction still has to clear the passive activity rules of section 469 before it offsets non-rental income.
Amadae runs this decision as part of its Form 3115 catch-up work: it screens the property, computes the section 481(a) adjustment or the amended-year figures, and prepares and files whichever return the rule requires.