You cannot fix it. If you are the one who is supposed to claim the child for 2019, and she has already used his SSN on a return--which it seems she did for the stimulus -- then all you can do is print, sign and mail your own return, and let the IRS sort it out.
You may get the last laugh--because since she already filed for the stimulus -- probably using the non-filer site -- and plans to file an actual tax return, her tax return will be rejected too, and she will have to paper file.
**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.**
