Editing Medicare (United States) (section)

===Unfunded obligation===
Medicare's unfunded obligation is the total amount of money that would have to be set aside today such that the principal and interest would cover the gap between projected revenues (mostly Part B premiums and Part A payroll taxes to be paid over the timeframe under current law) and spending over a given timeframe. By law the timeframe used is 75 years though the Medicare actuaries also give an infinite-horizon estimate because life expectancy consistently increases and other economic factors underlying the estimates change.

As of January 1, 2016, Medicare's unfunded obligation over the 75-year time frame is $3.8 trillion for the Part A Trust Fund and $28.6 trillion for Part B. Over an infinite timeframe, the combined unfunded liability for both programs combined is over $50 trillion, with the difference primarily in the Part B estimate.<ref name="ReferenceB"/> These estimates assume that CMS will pay full benefits as currently specified over those periods though that would be contrary to current United States law. In addition, as discussed throughout each annual Trustees' report, "the Medicare projections shown could be substantially understated as a result of other potentially unsustainable elements of current law."{{Citation needed|date=March 2025}} For example, current law effectively provides no raises for doctors after 2025; that is unlikely to happen. It is impossible for actuaries to estimate unfunded liability other than assuming current law is followed (except relative to benefits as noted), the Trustees state "that actual long-range present values for (Part A) expenditures and (Part B/D) expenditures and revenues could exceed the amounts estimated by a substantial margin."{{Citation needed|date=March 2025}}