The child tax credit (CTC) is a $1,000 partially refundable federal income tax credit for each qualifying child under age 17. In 2007, tax filers may claim a refundable credit (over and above any tax liability) equal to 15 percent of the excess of earnings over $11,750, up to the $1,000 maximum per child. The earnings threshold means that families with very low incomes get no benefit from the credit, and others will receive only a partial credit. This brief analysis shows that many families with young children tend have lower incomes and are thus left out. In 2007, 30 percent of qualifying children under age 2 in working families had family incomes too low to benefit from the full credit, compared with 27 percent of children overall and 24 percent of children 10 and older.