What is the final date to send/pay amended taxes file?

[MichaelL1]

The due date on the 2018 return is 4-15-2019.

If you have a refund coming you can actually file an Amended return for up to three years from the due date or 4-14-2022.

Of course there is interest if you owe money, or get money back, so if you are going to owe on an Amended return, I would file and pay it by 4-15-2019 if you can.