I received a bill fro the IRS for exceeding the maximum contribution for a Roth IRA for 2018

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.

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