You can not amend prior years. The omission has gone on for too many years. This is a change in accounting methods. It requires filing Form 3115 for the year of change. The missed depreciation is subject to IRC 481 as to when it is included In taxable income
from reg 1.481-1
(2) If a change in method of accounting is voluntary (i.e., initiated by the taxpayer), the entire amount of the adjustments required by section 481(a) is generally taken into account in computing taxable income in the taxable year of the change, regardless of whether the adjustments increase or decrease taxable income. See, however, §§ 1.446-1(e)(3) and 1.481-4 which provide that the Commissioner may prescribe the taxable year or years in which the adjustments are taken into account.
consult a pro
