No, you do not need to file an amended return to correct prior depreciation for your rental property.
If you entered an in-service date for the current year, but started renting the property in 2011, your total depreciation for the property is incorrect.
Residential rental property is depreciated equally over 27.5 years, and the depreciation per year is the same. Because you began renting the property mid-year, the amount of depreciation was pro-rated based on the number of months it was rented. This calculation would be correct, even though the total for the property does not include prior deprecation.
Next year, you will need to adjust the prior depreciation to include what was omitted this year.
You will need the Depreciation Report from the workpapers of the tax return when you last rented the property. TurboTax creates this report as a worksheet included in your complete tax return (see screenshot #1 below - click to enlarge). Most tax preparation services provide a similar report.
Total accumulated (or "prior") depreciation on this report is the total of the Current and Prior columns. This is the amount you would adjust next year (screenshot #2).
