My first suggestion would be to check with the HR Department of your former employer (if possible) to see how they will be they will be handling the repayment. You may require a corrected W2. IRS Publication 529 details of repayments of Relocation Allowances. Also, I found someone who had a similar case to yours in the community and I will share that link below:
https://ttlc.intuit.com/community/after-you-file/discussion/relocation-lumpsum-payback-to-previous-e...
I will also recommend that you review the Repayment Section (Page 36) of IRS Pub 529.
https://www.irs.gov/forms-pubs/about-publication-529
If you find this answer helpful, give me a thumbs UP!!!
