Site: nolo.com
... However, for 2021 only, the age of a qualifying child is increased to children under age 18 at the end ... However, the Tax Cuts and Jobs Act greatly increased the amount you can earn and still receive the credit ... For 2021 only, the child tax credit is increased to:
$3,600 for every child under age 6, and
$3,000 ... The increased credit amount is phased out for married couples with incomes over $150,000 and single parents ... For example, if you have one child over age 5, you're entitled to a $1,000 increased credit for 2021. ...