This flow chart may help individuals who are still working at age 65 or older decide if they should sign up for Medicare and/or continue to contribute to a qualified Health Savings Account. Considerations are different for those who work for employers with 20 or more employees versus those who work for smaller employers as well as those who are taking Social Security benefits. One of the most important things to know is if someone has creditable coverage, including creditable drug coverage. If not, and they sign up later, they may face lifelong penalties. There also may be severe tax consequences for those contributing to an HSA while receiving Medicare Part A, and Part A coverage is mandatory and retroactive for 6 months before they signed up for Social Security benefits or age 65, whichever is later.