Tax Relief Extension Act of 2003 - Amends the Internal Revenue Code to extend provisions concerning: (1) parity in the application of certain limits to mental health benefits; (2) the credit for electricity produced from certain renewable resources; (3) the work opportunity credit; (4) the welfare-to-work credit; (5) the taxable income limit on percentage depletion for oil and natural gas produced from marginal properties; (6) qualified zone academy bonds; (7) the cover over tax on distilled spirits; (8) the deduction for corporate donations of computer technology; (9) the credit for qualified electric vehicles; (10) the deduction for clean-fuel vehicles and certain refueling property; (11) the deduction for certain expenses of school teachers; (12) the availability of medical savings accounts; (13) the expensing of environmental remediation costs; (14) the expansion of the work opportunity tax credit to the New York Liberty Zone; (15) the temporary special rules for taxation of life insurance companies; (16) certain tax incentives for investment in the District of Columbia; (17) the combined employment tax reporting program; (18) transfers of excess pension assets to retiree health accounts; and (19) IRS user fees.
Adds to the definition of taxable vaccines any vaccine against hepatitis A and any trivalent vaccine against influenza.