You are not eligible to make contributions to an HSA after you have Medicare.
To avoid a tax penalty, you should make your last HSA contribution the month before your Part A coverage begins.
Premium-free Part A coverage will go back (retroactively) six (6) months from when you sign up for Part A coverage or apply for benefits from Social Security or the Railroad Retirement Board, but no earlier than the first month you are eligible for Medicare.
Depending on how you become eligible for Part A, the retroactive period may be different. We can help you plan ahead so that you avoid any potential tax penalties. In addition, if you are still working and have employer coverage through work, contact your employer to find out how your employer’s coverage works with Medicare.