for 2022, since there was no cap on Medicare wages, you use $30K to determine Medicare refund @1.45% or $435. For Social Security, you might have gone over the maximum of $147,000 in compensation for Social Security purposes for the year. You'll need to determine what your gross compensation was for Social Security proposes. If $147K or less the full $30K is eligible for the refund. If $177K, or more then none of the $30K is eligible for the refund. For example, if gross compensation for Social Security purposes was $150K. you didn't pay social security taxes on $3,000 so only $27,000 is eligible for Social Security refund @6.2%. There are often differences between compensation for boxes 1, 3, and 5.
Form 843 instructions
Refund of excess social security, Medicare, or RRTA tax. If
you are claiming a refund of excess social security, Medicare, or
RRTA tax withheld by one employer, you must, if possible,
attach a statement from the employer. The statement should
indicate the following.
• The amount, if any, the employer has repaid or reimbursed
you for excess taxes withheld.
• The amount, if any, of credit or refund claimed by the
employer or authorized by you to be claimed by the employer.
The employer should include in the statement the fact that it is
made in support of your claim for refund of employee tax paid by
the employer to the IRS.
If you cannot obtain a statement from the employer, you
should attach a statement with the same information to the best
of your knowledge and belief and include in the statement an
explanation of why you could not obtain a statement from the
employer. Attach a copy of your Form W-2 to prove the amount
of social security, Medicare, or RRTA tax withheld.
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How to recoup income taxes paid on that $30K in 2022.
on your 2023 return you:
1) can take as a deduction on Schedule A line 16 and denote it as IRC 1341 repayment OR
2) recompute the taxes for 2022 by reducing box 1 of your W-2 by $30K. The reduction in taxes is what you can claim as a credit on your 2023 1040 on schedule 3 line 13b
