We just got through to the IRS due to 3 of these letters being received so far and have the following to report (hope it helps):

• the letter is legit
• 2 of the notices were due to estimated payments sent by clients that we didn't report.
• 1 was due to an amended return that is not processed yet. In the case of the amended return, the client does owe that amount sent but since the amendment has not been processed the IRS doesn't realize it.
• If clients don't go online to update their banking within 30 days, paper checks will be mailed out 6-8 weeks later.
• To update banking they go to their IRS account (if they have one), go to Profile at the top of the page then Update Banking on the left.