That was a boo-boo actually. By the tax filing deadline (which was Apr 18 last year) you would have known by then. What I would suggest you do is one of two things (and doing it later won't prevent you from going ahead with your 2017 taxes). Either amend the 2015 tax return to show the property converted to personal use on Dec 31st of 2015. Or you can amend the 2016 return and show the property converted to personal use on Jan 1, 2016. You want to do this to stop depreciation for the entire 2016 tax year that you couldn't rent it out, even if you wanted to. WHen it comes time to sell the program (which you did in 2017) that year's worth of depreciation can hurt.
But first, lets see what the yearly depreciation is, to see if it's even worthwhile to you. I assume you have a printout of your 2015 return. If you don't, then open up the 2015 tax file (using TurboTax 2015 if you didn't save it in PDF format). What you need is the printout or PDF that shows you everything; worksheets and all. Not just the forms "required to filing" or the forms "to keep for your records". You want everything. The PDF could easily be over 100 pages too. So don't let that surprise you.
What you are looking for is the 2015 IRS Form 4562 for that property. There will be three of them for that property. One prints in portrait format, and the other two print in landscape format. Of the two that print landscape, you want the one titled "Depreciation and Amortization Report".
On that 4562 you will at a minimum, see the property itself listed there. If you've done any property improvements they will be listed also. Under the "cost - net of land" column is the value of the structure. The "land" column shows the value of the land.
The "prior depreciation" column shows the amount of deprecation taken *BEFORE* 2015. Then the "current deprecation" column shows the deprecation taken *IN* 2015. In order to get the total depreciation taken, you have to add those last two columns together. That total is what you have to recapture and pay taxes on, in the year you sell the property.
Now we've been looking at the 2015 return. So in order to get the "correct" figure, if you deprecated it in 2016 (which would have been a bad idea since there is no rental income in 2016 to take that depreciation against) you need that same 4562 from the 2016 tax return.
What's the current year's deprecation you see on the 2015 form 4562? Let's see if this is worth an amendment or not.
