Reservists Pay Security Act of 2004 - Entitles Federal employees who are absent from their positions while on active duty in the uniformed services or the National Guard to receive the amount of their basic pay which, when taken together with their military pay and allowances, is no less than the amount of pay that they would have earned if there had been no interruption in their civilian employment.
Expands the reemployment rights of Federal employees on active duty in the uniformed services.
Requires the Office of Personnel Management to prescribe regulations to carry out the provisions of this Act.
Makes this Act retroactive to pay periods beginning on October 11, 2002, subject to the availability of appropriated funds.
Authorizes appropriations.