Today, there is no "simple" version of Medicare. But Medicare drives most hospitals' business and continues to affect the private managed care side of the industry, so providers tolerate it because they have no choice. The increasing complexity of payment calculations has created an environment where important payment details are embedded in thousands of pages of "final rules" and "manuals." Following are five commonly misunderstood components of the inpatient and outpatient prospective payment systems -- and how providers can minimize their impact: 1. Medicare severity-adjusted diagnosis-related groups, 2. what is a "specialty hospital"?, 3. a tale of two payment technicalities, 4. no "bundle of joy," and 5. understanding the nuances of billing. Therefore, it's more important than ever for healthcare financial leaders to know what their organizations should be paid and understand how Medicare payment systems can be interpreted to the provider's detriment.