The IRS is sending out the CP56 or CP53E letters to anyone who had an overpayment from last year, saying it "can't process your refund" because there is no bank account number for direct deposit, even if the overpayment is being applied to next year's taxes and you did not request a refund. THIS IS AN IRS SYSTEM GLITCH, NOT A SCAM.
I just confirmed this by checking my IRS account online. The overpayment was applied to next year, yet IRS sent me the letter saying I had to log on and give them a bank account number because they were "unable to process my refund."
I hear online about other people getting the letter who were not even owed a refund, and many people are justifiably concerned about getting the letter, thinking that someone else fraudulently submitted a return under their name, etc. That is not the case. This is an IRS system bug.