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CAUTION

You may not file a refund claim to correct Tier 1 Employee Additional Medicare Tax actually withheld from employees.

4 Instructions for Form CT-1 X (Rev. 4-2025)

Department of the Treasury Internal Revenue Service Center Cincinnati, OH 45999-0007

PDSs can’t deliver to P.O. boxes. You must use the USPS to mail an item to a P.O. box address. Go to IRS.gov/PDS for the current list of PDSs. If you file Form CT-1 X using a PDS, send it to the following address.

Ogden-Internal Revenue Submission Processing Center 1973 Rulon White Blvd. Ogden, UT 84201

Use this address even though Form CT-1 X mailed through the USPS goes to Cincinnati.