I personally havent run across this situation, but this article in TurboTax explains the different ways it may happen. You may want to ask the employer what to expect.
https://ttlc.intuit.com/community/taxes/discussion/repayment-of-signing-bonus-in-subsequent-year/00/...
♪♫•*¨*•.¸¸♥Lisa♥¸¸.•*¨*•♫♪
