To amend the Internal Revenue Code of 1986 to increase the child credit for children under the age of 6, and for other purposes.

Child Tax Credit Improvement Act This bill amends the Internal Revenue Code, with respect to the child tax credit, to: (1) allow taxpayers an increased $3,600 tax credit for each young child under the age of six (young child tax credit), subject to specified limitations based on adjusted gross income; (2) require the Department of the Treasury to establish a program to make advance payments of the young child tax credit; (3) modify the refundable portion of the child tax credit; and (4) require annual inflation adjustments for both the child tax credit and the young child tax credit.