My 2018 IRA contribution was not post marked before April 15 but I claimed it on my taxes. Must I file an amended return?

[SweetieJean · Accepted solution]

Yes you do.

https://ttlc.intuit.com/questions/4726714-amend-2018-return

If you actually mailed a check to the IRA plan administrator, contact them to either apply it to a 2019 IRA, or return it to you.