In context
§481(a) prevents items from being duplicated or omitted when an accounting method changes. The adjustment equals:
(Total depreciation that would have been claimed from placed-in-service date through the year before change, under the new method) — (Total depreciation actually claimed under the old method during the same period)
For missed depreciation (cost segregation on a previously-acquired property), the §481(a) is negative — additional depreciation deducted in the year of change. The taxpayer does not amend prior returns; the cumulative correction is captured in a single year.
§481(a) adjustments of $50,000 or more positive are spread over four tax years under Rev. Proc. 2015-13. Negative adjustments and smaller positive adjustments are taken fully in the year of change.
The §481(a) calculation for bonus depreciation uses the bonus rate that applied in the placed-in-service year — not the current rate. A 2023-placed property cost-segregated in 2026 captures 80% bonus on the accelerated buckets, not 100%.
See /form-3115/ for the topic hub.