You are not able to make changes to a pending return. To make corrections or changes to your pending return, wait until your return's either been accepted or rejected.
If your return is rejected you can then add the forms. Once your return has been accepted, you will not be able to make any changes until after your refund has been processed. Amending your return means filing a new form, 1040X. This is only required in certain situations. In other situations, you can change your original return and you should not file a new form. Please click Do I need to amend? to learn more.
You should not try to amend your return until it has been fully processed and you have received your refund or your payment has cleared. Amended returns do not “catch up” to your original returns and replace them. They are processed as two separate returns.
Please click How do I amend my 2019 TurboTax Online return? to learn more.