Tax Relief for Working Caregivers Act of 2007 - Amends the Internal Revenue Code to: (1) increase from $15,000 to $75,000 the taxpayer adjusted gross income amount at which the tax credit for household and dependent care expenses is phased down; and (2) allow such credit for a physically or mentally incapacitated parent (or an ancestor of such parent) of the taxpayer who is a dependent of such taxpayer.