you don't get to pick and choose the years to correct. it's all of them.
I'll repeat
Once an incorrect accounting method has been used for two years, a Form 3115 is required to change accounting methods back to a correct method, or in this case, since not taking depreciation is incorrect, to begin taking depreciation a Change in Method form must be filed.
Generally, the IRS can include returns filed within the last three years in an audit. If we identify a substantial error, we may add additional years. We usually don't go back more than the last six years.
note that without correction that excess depreciation is subject to section 1250 recapture. so it maybe that when you sell you'll be paying more in income taxes.
you cannot just change current and future depreciation to correct excess prior depreciation That too can open you to audit. If the iRS audits your returns for any open year and corrects the error not only may you owe taxes but potential penalties and interest. There are no penalties or interest if you correct using form 3115.
