Unfortunately, this is NOT a situation that qualifies for Form 3115. You can only amend the 'open' years to correct the missed depreciation.
For your current year return, you just edit the assent and change it to the correct Basis. And for the "prior depreciation", you need to enter what you SHOULD have claimed for the prior depreciation.
@jcon95482 wrote:
when it was converted to a rental property.
When you converted it, you needed to use the LOWER of (1) the Basis at that time (usually purchase price, plus cost of improvements, minus any depreciation such as from a Home Office) or (2) the Fair Market Value at that time of conversion.
Is that possibly what the discrepancy is? Was the Fair Market Value lower than the Basis?
If your situation required you to use the Fair Market Value amount, TurboTax is NOT set up for that situation and you should consider a good tax professional.
