Medicare Early Access Act of 2004

Medicare Early Access Act of 2004 - Amends title XVIII (Medicare) of the Social Security Act, as amended by the Medicare Prescription Drug, Improvement, and Modernization Act of 2003, to add a new part E (Purchase of Medicare Benefits by Certain Individuals 55 to 65 Years of Age).

Provides access to Medicare benefits for individuals 55 to 64 years of age who do not have coverage under a Federal health insurance program or under a group plan.

Requires enrollees to pay a premium to receive Medicare coverage. Requires the Secretary to base the premium on the Secretary's estimate of the average, national annual per capita amount of the cost of providing services to the population.

Allows early retirees with access to retiree coverage to enroll under this part while keeping their Federal or State COBRA (Consolidated Omnibus Budget Reconciliation Act of 1985) continuation coverage. Allows an employer that offers employment-based retiree health coverage to an individual who enrolls under this part to modify such coverage to provide for: (1) employer payment of items and services for which payment may not be made under Medicare; and (2) employer payment of 25 percent of the monthly premium applicable to the individual after enrollment.

Creates in the Treasury the Medicare Early Access Trust Fund to hold the premiums collected under this Act and to support the new program.

Amends the Internal Revenue Code to allow program enrollees to receive a 75 percent advance, refundable credit to offset premium costs (thus requiring program enrollees in the Medicare buy-in to be responsible for 25 percent of the monthly premiums).