Flat Tax Act of 2003

Flat Tax Act of 2003 - Amends the Internal Revenue Code to repeal current tax provisions for individuals and businesses and replace them with provisions for a flat tax of 20 percent of the income of individuals and businesses.

Allows an individual: (1) a standard deduction, with an inflation adjustment; (2) limited charitable contribution deductions; and (3) a limited deduction for home acquisition indebtedness.

Allows deductions to a business for: (1) the cost of business inputs (the cost of specified goods, services, travel, entertainment, and lobbying and political expenditures); (2) compensation paid to employees; and (3) the cost of personal and real property used in business activities.

Repeals the estate, gift, and generation-skipping transfer taxes. Repeals provisions concerning: (1) financing of presidential elections; and (2) coal industry health benefits.