File an amended or corrected return using Form 1040X
(PDF), Amended U.S. Individual Income Tax Return, as soon as possible.
Include copies of any schedules that have been changed or any Form W-2
(PDF) you did not include.
If you return the refund check with a letter of explanation, a refund in the correct amount will be issued when the IRS processes the amended return.
Write "Void" in the endorsement section of the check, and within 21 days after receiving it, return the check a letter of explanation to the Service Center where you file your amended return.
Allow the IRS 8-12 weeks to process the Amended return.