Deductions & credits
It depends.
When you entered him as a dependent, you should have marked him as living with your for the entire year even though he was born towards the end of the year (congratulations!).
Check your return.
If you do not see him listed as a dependent on page 1 of your Form 1040, then he may not have been claimed. You will also need to confirm if box 4 is checked for the child tax credit. If it is not, you will need to amend your return.
See the attached link for instructions to help you amend your return. You will need to amend your federal return and your state return, if applicable.
In regards to the stimulus payment, yes, you should have received an additional $500 for him as a dependent.
When you file your return in 2020, you will have the opportunity to report the amount of the stimulus check(s) you did receive.
Since it was less than what you were entitled to, you will receive a credit on your tax return.
