@ravuun wrote:
Which 1040 would she fill out then? She said the 1040X wasn't the same form that she had filled out to amend her status previously.
The "non-filer" form is technically a form 1040 tax return claiming zero income and the rebate. You are correct that your daughter must have not checked "I can be claimed as a dependent by someone else."
Your daughter needs to prepare an amended tax return—that's a new form 1040 containing the necessary changes along with a 1040X which acts as a cover page that summarizes the changes. In this case, she will check the box for "I can be claimed as a dependent" and will not get the rebate. The 1040X should show that she owes a repayment of up to $1800.
It sounds like you would then send the amended 1040 and 1040X to the Advocate rather than filing it in the normal way, but you should follow whatever instructions they have given you.
