As most of us know, an individual who is enrolled in Medicare Part A or B is ineligible to contribute to a health savings account. For that reason, insurance agents often advise their clients to postpone their enrollment in Medicare until they retire and drop their group health coverage.

With Medicare Part B, this is no big deal. When an individual delays enrollment in Part B because she’s covered by an employer’s group plan, she has an eight-month “special enrollment period” during which she can sign up after losing her group coverage.

With Medicare Part A, though, it’s not so simple. A little-known rule in the Social Security Administration’s "Program Operations Manual System," an SSA handbook designed for internal use by SSA employees in processing claims, says that anyone who opts out of Medicare Part A also forfeits all past and future Social Security retirement benefits. This means that seniors would stop receiving their Social Security check and would be required to repay any benefits received prior to disenrolling from Part A.