I filed my 2018 tax return and later made traditional IRA contributions for 2018. Do I have to amend my 2018 return, or just file Form 8606? Do I also amend state return?

 
maglib
Level 11

After you file

Since a qualified traditional IRA investment would reduce your taxable income yes you would have to choose to amend your returns for both federal and state purposes.  This may result in tax savings.

https://ttlc.intuit.com/replies/3288565

**I don't work for TT. Just trying to help. All the best.
***Say "Thanks" by marking as BEST ANSWER and clicking the thumb icon in a post and that I solved your question
**Mark the post that answers your question by clicking on "Mark as Best Answer"
I am NOT an expert and you should confirm with a tax expert.