Investors & landlords

You are correct- to resolve this you probably need to file a 3115.  Upon disposition, you must recapture depreciation allowed or allowable (meaning the amount missed gets included here which is not a good result.)

If you only filed one year with missed depreciation, you can choose to go back one year and amend, or file a 3115.  That's because an error becomes your "accounting method" when done for 2 years or more, then the option goes away and you must file a 3115.

Form 3115 is not supported for e-file or TurboTax Online, so use a Desktop version and paper file. 

Here is an article you may find helpful: What should I do if I didn’t take depreciation on my rental property?