There was no "stimulus tool" to get the stimulus in 2021. The only way to get the stimulus payments in 2021 was to use the recovery rebate credit on a 2020 tax return. You probably answered something incorrectly since you are confused. As to whether your tax return will be rejected, we cannot say. The IRS will begin to accept/reject e-files on January 24.
Do not try to change anything on your return. Do nothing to it. Wait to see if it is accepted or rejected. If it is rejected you can make corrections and re-file it. If it is accepted with your mistake you will just have to wait and see what they do. It could go under review and take a long time to be processed. They will probably catch a mistake you made with the stimulus but you will just have to wait it out.
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
