If your child had a valid SSN and you claimed them as your Dependent, you may have received a Child Tax Credit.
If they were your Dependent in prior years on your return the 'not valid for employment' SSN status does not affect you receiving the credit.
Look over your printed or saved copy of your returns to see if you got the credit.
If you did not receive the Child Tax Credit in 2017, 2018 or 2019, you can Amend your Returns for those years.
Click this link for instructions on How to Amend a Prior Year Federal Return.
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