You report the repayment as a business expense on Schedule C. Enter it under other expenses (not in one of the fixed categories) with a short description such as "Repayment of 2020 overpayment."
Thank you for answering my question. I am guessing that TurboTax provides the option you mention : other expenses, correct?
Q. I am guessing that TurboTax provides the option you mention : other expenses, correct?
A. Yes. That entry allows you to enter a brief description, which will appear in Part V of Schedule C.
As an alternative, you could enter it as "Returns and allowances" (entered in income section, rather than expenses section of the TurboTax self employment interview) which puts it on line 2 of Schedule C.
Either entry is OK.