The United States Court of Appeals for the District of Columbia Circuit recently held in Saint Francis Medical Center v. Azar that Medicare’s reopening regulation, which prohibits providers from seeking to revise payment determinations after three years, including the “predicate facts” that support those determinations, does not apply to cost report appeals. The Saint Francis decision has broad implications. Many categories of Medicare reimbursement rely upon factual determinations that are made in so-called base-years. For example, the number of reimbursable full-time equivalent (“FTE”) residents claimed by teaching hospitals cannot exceed the number claimed on their 1996 cost reports—the base year. If these years-old fact determinations were made in error, they can now be revisited on appeal and, potentially, increase future year reimbursements. In addition, the providers in the Saint Francis case allege that the original IPPS standardized rate, which was determined in 1983, was improperly calculated. The D.C. Circuit’s decision now paves the way for all providers to file such appeals for current and future cost report years. King & Spalding recommends that its clients consider filing such “standardized amount” appeals, but just as important, we recommend that clients begin to inventory whether there may be costreporting errors in past years that affect base-year determinations that now can be challenged on appeal.