It's an erroneous refund if you receive a refund you're not entitled at all or for an amount more than you're entitled to. 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, but no later than 21 days, to the appropriate IRS location. The location is based on your state of residency. Use the mailing address listed in the About Form 3911 page for the state you live in. Don't staple, bend, or paper clip the check. Include a note stating "Return of erroneous refund check" 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, but no later than 21 days, to the appropriate IRS location. The location is based on your state of residency. Use the mailing address listed in the About Form 3911 page for the state you live in. Write on the check/money order: “Payment of Erroneous Refund,” the tax period for which the refund was issued, the account type ((IMF) individual or (BMF) Business) 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. Cashing an erroneous refund check 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) (see telephone assistance for hours of operation) to explain why the direct deposit is being returned. Interest may accrue on the erroneous refund. 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.