MOOP stands for "maximum out-of-pocket" costs and is a limit on annual out-of-pocket expenditures paid by a health plan enrollee for medical services that are covered by a health insurance plan. It is an important term in the context of Medicare Advantage Plans, which must set an annual limit on an individuals out-of-pocket costs, known as the maximum out-of-pocket (MOOP). Once an individual reaches this amount, they will not owe cost-sharing for Part A or Part B covered services for the remainder of the year. The MOOP includes all cost-sharing (deductibles, coinsurance, and copayments) for Part A and Part B covered services that an individual receives from in-network providers. Part D cost-sharing does not count towards the plans MOOP. The MOOP is a tool to protect a health plan enrollee from catastrophic medical costs that can occur despite the presence of health insurance coverage.