Child Support Enforcement Act of 2005 - Amends the Internal Revenue Code to: (1) allow a custodial parent (a parent entitled to receive child support) a refundable tax credit for unpaid child support; and (2) include in the gross income of any taxpayer who is delinquent in the payment of child support the amount of such unpaid child support.
Prohibits the Internal Revenue Service from selecting a tax return for audit based upon any discrepancy between the tax returns of a custodial parent and a taxpayer delinquent in the payment of child support.