You will need to contact our assistance line at (800) 829-1040 to receive information on the processing of your amended return. Amended/corrected returns are processed as quickly as possible. However, it could take 8 to 12 weeks to process an amended return.

References:

• Form 1040X (PDF), Amended U.S. Individual Income Tax Return
• Tax Topic 308, Amended

Source: www.irs.gov