If you enroll in Medicare Part A and/or B, you can no longer contribute pre-tax dollars to your HSA. This is because to contribute pre-tax dollars to an HSA you cannot have any health insurance other than an HDHP. The month your Medicare begins, your account overseer should change your contribution to your HSA to zero dollars per month. However, you may continue to withdraw money from your HSA after you enroll in Medicare to help pay for medical expenses, such as deductibles, premiums, copayments, and coinsurances.
