For a 2018 contribution? What type of letter (a CP xxx ) letter? What does it say?
I find that very unusual since Roth IRA contribution are not reported on a tax return at all - only the IRA custodian reports to the IRS and then that is on a 5498 form issued in May and it would take the IRS months to find a problem.
**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.**