Relief for Working Families Tax Act of 2003

Relief for Working Families Tax Act of 2003 - Amends the Internal Revenue Code with respect to the child care credit to: (1) make the 15 percent refundable portion of the child tax credit effective as of 2003 (currently 2005); (2) include combat pay within taxable income for refundable credit determinations; and (3) establish phased-in increases to the income threshold amounts for joint filers and for married filing separate filers (marriage penalty reduction). States that such amendments shall be subject to certain sunset provisions under the Economic Growth and Tax Relief Reconciliation Act of 2001.

Amends the Code to provide a uniform definition of "child."

Amends the Consolidated Omnibus Budget Reconciliation Act of 1985 to extend customs user fees.