There's some stuff missing from the expert's answers.
First, as stated, a foster parent is in the same legal position to claim a dependent as a biological parent, but only if the placement was by a court or agency authorized by the state. If it was a private placement, it may not qualify.
Second, you need the child's SSN to claim the $2000 child credit for a dependent. Without the SSN, you can claim a $500 credit for "other dependent."
Third, for 2021, if the child was born in 2021, it is not necessary for the child to live in your home more than 183 nights, only that they live in your home more than half the nights of the year since their birth. You can amend your 2021 return to claim the dependent, if you choose. For 2021, you would qualify for up to a $3600 child tax credit if you have the child's SSN, or $500 other dependent credit with no SSN.
