I received a letter from the IRS with this: "THIS IS NOT A TAX BILL. It shows the taxable interest paid to during the calendar year by the Internal Revenue Service. If you are required to file a tax return, report this interest as income on your return ..."
This feels like a 1099-INT, but it is not an actual 1099-INT. Where should I report this? 1099-INT, with the amount "Total Interest Paid or Credited" as Box 1?
Yes, enter it like a 1099-INT. Received from the IRS and the amount in Box 1. You do not need the actual 1099-INT to report your interest income.
It is clear how to report the taxable INTEREST.
But
Where is the CREDIT claimed?
Report it as though it was received on a 1099-INT. You simply put IRS or Department of the Treasury as the payer and enter your interest amount. Nothing else is needed.