If you discover you have made an error on your return, or you received another W-2 or 1099 in the mail after e-filing, you can correct the error only if the return has been rejected. If rejected, make any corrections and resubmit.
If your return was accepted, wait until you receive your refund before you do anything. The IRS will often catch simple omissions or minor mistakes. It is possible that they will correct the error for you and adjust your refund accordingly. If this is the case, you would not need to file an amended return.
If your return is already accepted, and the refund amount is incorrect or you need to add any additional forms, you must mail a paper Amended Return (Form 1040X). The IRS does not accept amended returns electronically.To create an amended return: