If it is a 2018 contribution prior to April 15, 2019, then yes, you must amend 2018 to report is either as a deductible contribution on the 1040 form or a non-deductible contribution on line 1, 3 & 14 on a 8606 form attached to an amended return.
A 2019 contribution will be reported next year on your 2019 tax return.
**Disclaimer: This post is for discussion purposes only and is NOT tax advice. The author takes no responsibility for the accuracy of any information in this post.**
