If your employer withheld too much Social Security tax in Box 4 or Medicare tax in Box 6, you will need to contact your employer for a refund of the excess FICA taxes withheld. Excess social security withholding occurs when Box 4 is more than 6.2% of Box 3 on your Form W-2 Wage and Tax Statement.
Excess Medicare withholding occurs when Box 6 is more than 1.45% of Box 5 on your Form W-2 (with the exception of those subject to the Additional Medicare Tax of 0.9%; see Questions and Answers for the Additional Medicare Tax for more information). The tax return can still be filed by either:
In situation (1), you would need to wait for the corrected Form W-2 from your employer, then see Form W-2 - Entering in Program. If you choose to use the Quick Entry process, be sure to scroll down to answer all questions, including to check Form W-2C, Corrected Wage and Tax Statement at the top of the form.
You are still able to file your return electronically.
In situation (2), you would need to complete and mail Form 843 to the IRS separately from your return. You are still able to file your return electronically. Please see the additional information outlined below.
Per IRS Instructions for Form 843, on page 1:
Purpose of Form
Use Form 843 to claim a refund or request an abatement of certain taxes, interest, penalties, fees, and additions to tax.
CAUTION! Do not use Form 843 to request an abatement of income, estate, or gift taxes. Do not use Form 843 to request a refund of income tax or Additional Medicare Tax. Employers cannot use Form 843 to request a refund or abatement of Federal Insurance Contributions Act (FICA) tax, Railroad Retirement Tax Act (RRTA) tax, or income tax withholding. Also do not use Form 843 to amend a previously filed income or employment tax return. Do not use Form 843 to claim a refund of agreement fees, offer-in-compromise fees, or lien fees.
On page 4:
Explain in detail your reasons for filing this claim and show your computation for the credit, refund, or abatement. If you attach an additional sheet(s), include your name and SSN, ITIN, or employer identification number (EIN) on it. Also attach appropriate supporting evidence. Include a statement that to the extent of equivalent amounts of underpayment and overpayment for the period(s) identified and established, the period(s) has (have) been used only once in a request to obtain the net interest rate of zero under section 6621(d). See Requesting Net Interest Rate of Zero on Overlapping Tax Underpayments and Overpayments, later, for more information.
On page 5:
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.
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.
Refund of social security and Medicare tax withheld in error. The same supporting evidence described above must be provided. If you are a nonresident alien, see Pub. 519 for additional information.
Note that any link in the information above is updated each year automatically and will take you to the most recent version of the document at the time it is accessed.