Yes, you should start claiming depreciation ASAP. You can file amended returns and take depreciation, but you can only go back to 2015 (which would have to be mailed on or before April 18. The 3115 would allow you take the depreciation you didn't take in the current year. It's not the easiest form to complete - you might want to seek some help with it. Also, I recommend you use TurboTax desktop so you can access the Forms mode to make sure you get your property set up and depreciation calculating properly. You can switch from Online to Desktop and you won't lose any work you've already done this year. To do so, see the following FAQ: <a rel="nofollow" target="_blank" href="
https://ttlc.intuit.com/replies/3302260">https://ttlc.intuit.com/replies/3302260</a>
