Wow. Thank you so so much DavidD66 for such a timely, thorough, and intelligible reply. I will definitely pursue Form 3115 to retroactively claim all the depreciation I should have taken on the room rental, and start including depreciation going forward.
Regarding "that is how you should determine the cost basis for your current rental of the entire house" --
I assume that for the period I rented a room, I would compute the starting cost basis using the FMV of my whole house (excluding land) when I first started renting the room, but only use the fraction of this based on the percentage of the house that I claimed as a rental. What's less clear is how I determine the basis now that I've started renting the entire home. The FMV has increased in the ensuing 10 years, but do I need to use the FMV from 10 years back when I started renting the room, or at the point that I started to rent the entire house (but reduced by the missing depreciation I could have claimed during the 10 years of room rental).
Also, the depreciation period is normally 27.5 years. Do I start counting from when I first rented just a room or at the point I switched to the whole house (that is, does the recovery period reset to 27.5 years at the point I switched)?
Lastly, I have always used, desktop TurboTax Deluxe for Windows, and cannot imaging using any other tax software. Thanks again. - T&J1
