Topic 161 – Returning an Erroneous Refund – Paper Check or Direct Deposit
If your refund was a paper Treasury check and hasn’t been cashed:

Write “Void” in the endorsement section on the back of the check.
Submit the check immediately to the appropriate IRS location listed below. The location is based on the city (possibly abbreviated) on the bottom text line in front of the words TAX REFUND on your refund check.
Don’t staple, bend, or paper clip the check.
Include a note stating “Return of erroneous refund check because (and give a brief explanation of the reason for returning the refund check).”
If your refund was a paper Treasury check and has been cashed:

Submit a personal check, money order, etc., immediately to the appropriate IRS location listed below. The location is based on the city (possibly abbreviated) on the bottom text line in front of the words TAX REFUND on your refund check. If you no longer have access to a copy of the check, call the IRS toll-free at 800-829-1040 (individual) or 800-829-4933 (business) (see telephone assistance for hours of operation) and explain to the assistor that you need information to repay a cashed refund check.
Write on the check/money order: Payment of Erroneous Refund, the tax period for which the refund was issued, and your taxpayer identification number (social security number, employer identification number, or individual taxpayer identification number).
Include a brief explanation of the reason for returning the refund.
Repaying an erroneous refund in this manner may result in interest due to the IRS.
If your refund was a direct deposit:

Contact the Automated Clearing House (ACH) department of the bank/financial institution where the direct deposit was received and have them return the refund to the IRS.
Call the IRS toll-free at 800-829-1040 (individual) or 800-829-4933 (business) to explain why the direct deposit is being returned.
When the amount of the refund (paper check or direct deposit) is different than what was expected, indicating the IRS changed the amount, a notice explaining the adjustment is mailed to your address of record. Please review the information in the notice to determine if the change to the refund is correct. A toll-free telephone number is included on the notice in case you require further assistance.

IRS mailing addresses based on the city (possibly abbreviated) located on the bottom text line in front of the words TAX REFUND on your refund check:

ANDOVER – Internal Revenue Service, 310 Lowell Street, Andover MA 01810
ATLANTA – Internal Revenue Service, 4800 Buford Highway, Chamblee GA 30341
AUSTIN – Internal Revenue Service, 3651 South Interregional Highway 35, Austin TX 78741
BRKHAVN – Internal Revenue Service, 5000 Corporate Ct., Holtsville NY 11742
CINCINNATI – Internal Revenue Service, 201 West Rivercenter Blvd., Covington KY 41011
FRESNO – Internal Revenue Service, 5045 E Butler Avenue, Fresno CA 93727
KANS CY – Internal Revenue Service, 333 W. Pershing Road, Kansas City MO 64108-4302
MEMPHIS – Internal Revenue Service, 5333 Getwell Road, Memphis TN 38118
OGDEN – Internal Revenue Service, 1973 Rulon White Blvd., Ogden UT 84201
PHILA – Internal Revenue Service, 2970 Market St., Philadelphia PA 19104