Unfortunately, Form 3115 can not be used. You should amend the 3 prior years.
Form 3115 can be used if there was NO depreciation taken, or it was taken using an incorrect procedure (such as depreciating it over 15 years), but it can NOT be used to correct the basis being depreciated (mathematical error).
Whenever you sell the property, makes sure you report the amount of depreciation that you actually took. When you do that, you will sort of be paying back the amount from your original error.
The IRS probably won't question any changes on your current tax return. The computers don't pick up that type of information very well (at least not yet), so unless an auditor looks at your tax return, it is very doubtful if any changes would ever be questioned. In the unlikely event they do, it should be a simple explanation of what happened.
