I used a cpa for my 2017 and 2016 returns. I suspect they werent done properly. Can i use turbotax to check those and file an amendment?

[SteamTrain]

Only wit difficulty......

1) would have to buy the 2017 and 2016 desktop software to install on a full Windows or MAC computer.   (Windows 7 or higher works .  For a MAC...MAC OSX 10.11 to 10.13 works best.   2016 on highest 10.14 version could be a problem)

2)  You'd have to reproduce your 2016 and 2017 tax return "exactly" as filed.   That could drive you nuts...

3)  Once it matches exactly....then you'd save, make a backup copy, and start an amended tax return to make the changes

4)  them print and mail in to the IRS (and state if needed)

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at #2, you could also just prepare it the way you think it should be to see what TTTX comes up with to see if it's worth your effort....but if you do decide to amend, you'd again need to use #2 -to-4 to amend