Turbotax is a DIY program that can handle decedent returns ... each tax year requires a separate program ...
You can't do a prior year return online or efile it, but you can buy the Desktop Download versions for 2015-2017 from Turbo Tax here. Be sure to pick the right one, Windows or Mac....
http://turbotax.intuit.com/personal-taxes/past-years-products.jsp
You will have to print and mail in prior year returns.
