Medicare Beneficiary Access to Rehabilitation Facilities Act of 2003

Medicare Beneficiary Access to Rehabilitation Facilities Act of 2003 - Amends title XVIII (Medicare) of the Social Security Act (SSA) with respect to prospective payment for inpatient rehabilitation services to direct the Secretary of Health and Human Services by regulation to define the terms "rehabilitation hospital" and "rehabilitation unit" in a manner fully consistent with all the rehabilitation impairment categories (except miscellaneous) used to classify patients into case-mix groups. Requires the Secretary to update these regulations periodically to ensure that they remain fully consistent with the rehabilitation impairment categories used to classify patients into case-mix groups.

Prohibits the Secretary from seeking to recoup any overpayment, take any enforcement action, or to impose any sanction or penalty, with respect to a rehabilitation hospital, or a converted rehabilitation unit insofar as such overpayment, enforcement action, sanction or penalty, is for failure to satisfy the requirement that 75 percent of the patients of the rehabilitation hospital or converted rehabilitation unit be in one or more of ten listed treatment categories (the 75 Percent Rule).