Our best advice is to leave the space blank if it will let you or enter dummy social security numbers for your parents. You could enter 999-88-9999 and 999-87-9999 as "dummy" social security numbers so you can finish your return. Then you must print the return and "white out" the dummy social security numbers and write in that space "NRA". Then you will need to mail your return. You cannot e-file.
For instruction about how to print and mail your return, use the following link. https://ttlc.intuit.com/replies/3401713
