We had a baby in 2019 and included him in our 2019 taxes, which we filed on 4/3/20. Our stimulus check didn't include the extra $500. How do we get the $500 from the IRS?

If you did not receive the full amount of the Stimulus Payment that you were entitled to receive, on your 2020 taxes you will be able to reconcile the amounts between what you should have received and what you did received and receive the remainder of the Stimulus Payment. 

Presently, the IRS has not set up a process to request the additional entitled payment amount this year.