@KNERD -
Congress passed the law that CTC and EITC benefits require the SSN to be issued prior to the due date of the return.
unfortunately, the 2018 and 2019 amendments will be denied since the SSN was issued after the due dates for these returns.
for 2020, if the SSN issue date was prior to May 15, 2021, you can amend and it should be accepted. if the SSN issue date is after May 15, 2021, the amendment will be denied.
As mentioned above, you can still amend for the $500 other dependent credits. Every dependent is eligible for up to $500, it is just that there is an additonal credit - called the child tax credit - for children under the age of 17. So when we state 'other' - we don't mean your other child, we mean the 'other' tax credit.
Further, for 2018, the deadline to submit amendments was April 15, 2022, so it is too late.
for 2019, the deadline to submit amendments is July 15, 2023.
