I had a baby in March 2020, how do I file to get his stimulus money?

Did you add your baby under My Info?  Be sure when it asks how long your child lived with you that you pick THE WHOLE YEAR (which is acceptable for newborns) and not just the number of months.  Go back and double check that.

The Stimulus Checks are really based on your 2020 return we are filing in 2021.  So any amount you already got will be reconciled on your 2020 return line 30.  If you didn't get a Stimulus Check (and qualify) or you qualify for more it will be added to your 2020 return.  But the good news is if they paid you too much they won't take it back.

Just file the 2020 return as usual ... enter the child in the MY INFO section ... READ these screens carefully ...