Most of the time, that's a repayment for compensation like sign-on bonus or other types of incentives or benefits that bind the individual to serve the company with satisfactory performance for a certain period of time.  Such repayments are governed by Claim of Right and may be taken as a credit (based on difference in tax in the prior year) or I/D not subject to 2% but the amount of repayment must exceed $3,000.