Simple Tax for Seniors Act of 2004 - Directs the Secretary of the Treasury to make available to taxpayers age 65 or older a new income tax form to be known as "Form 1040S" which shall be as similar as practicable to Form 1040EZ. Allows use of this form without regard to the amount of the taxpayer's taxable income or even if the taxpayer's income includes social security income, distributions from qualified retirement plans, interest and dividends, or certain capital gains and losses.