Incorrect W-2 that can't/won't be corrected
My issue is I received a W-2 from my company's disability carrier for their payments to me (and included in taxable income) and filed my 2020 taxes. In 2021, I received a bill from the carrier as they over-paid me and I had to reimburse them. The carrier stated they will not issue me a revised W-2 for 2020 with the corrected income.
I know if I just adjust the W-2 on the amended return it will kick out as it doesn't match the W-2 the IRS has. How do I amend my tax filing?