W-2 after same-year signing bonus repayment

Hi, I received a $30,000 signing bonus in 2023 which I repaid in full (gross amount, including all taxes: federal, state, Medicare, Social Security) as I left the company early. The repayment was done in 2023.

 

The employer issued a W-2 that adjusted all boxes as if I have never received this bonus. However, I repaid the full gross amount, as mentioned above. They have not provided any refund for any of the taxes I repaid.

 

I want to submit Form 843 to recover Medicare and Social Security taxes that I overpaid; also, I want to make sure that I receive as much refund as possible for the remaining taxes (federal, state).

 

That said, I would appreciate your help with some questions:

  • Should the 2023 W-2 include the amount of over-collected taxes (federal, state, Medicare, Social Security) that I repaid but never received? If yes, which W-2 Boxes should be adjusted? It looks to me that the W-2 is incorrect.
  • Can I still file IRS Form 843 for Social Security and Medicare refund if the W-2 does not include those taxes in Boxes 4 and 6?