I think you mean you should have filed a form 1040NR for a non-resident but you filed the form 1040 instead. If so, you need to prepare the non-resident form 1040NR. You can do this by using Sprintax . Wait to receive your refund, as there is a chance your return will be changed or rejected. Then go on line and prepare a form 1040-X (amended U.S. income tax return) Form 1040-X . Complete the personal information at the top of the form and then go to part II on the second page and enter an explanation that you filed the form 1040 in error that it should have been a form 1040NR. Sign, then send both forms to the address listed on the instructions to form 1040-X Instructions to form 1040-X . On the form 1040, write "Original Return" on the top of it