To amend from Form 1040 to 1040NR, here are the steps:
-If you are considered as a nonresident, as TurboTax does not support the NR form, you are recommended to use our affiliated partner, Sprintax to complete your 1040-NR filing.
1. Download the Form 1040-X from IRS website ( see below). On the front page of Form 1040-X, enter your name, current address, and social security number (SSN) or IRS individual taxpayer identification number (ITIN)
2. Do not enter any other information on page 1.
3. Do not complete Parts I or II on page 2 of Form 1040X.
4. Enter in Part III the reason why you are filing Form 1040X.
5. Complete a new or corrected form 1040-NR by using Sprintax, see above.
6. Across the top of the 1040-NR, write “Amended”
7. Attach form 1040-X to the back of Form 1040X
For more information, see:
https://www.irs.gov/pub/irs-pdf/i1040x.pdf - instructions
page 5 under Residents and Nonresidents