yes and no
you can not amend a return to change ITIN to SSN once it's filed HOWEVER for stimulus
- The stimulus payments are really based on your 2020 tax return (income, dependents, etc).
- The IRS is using either 2018 or 2019 – whatever is available - to ESTIMATE that payment
- When you file next year there will be a “settle up” section on the tax return.
- If you are due more stimulus (and this would include where you simply never received it), you will receive it through the 2020 tax filing as an additional refund
- If you received too much stimulus (not the issue here), by law , you are not required to return it
your only path forward is to use spouse's SSN number on the 2020 tax return; the stimulus will come through at that time as an additional refund on your taxes
