An HSA works like a tax-free savings account. You have to be enrolled in a high-deductible health plan to set up an HSA, and you cannot be on Medicare.
When you sign up for your health plan during open enrollment, you decide how much money you want taken out of your paycheck to go into your HSA. Some employers may also contribute to your account
The money in your HSA must go to pay for medical care. If you do not spend all the money in your HSA within a year, the money stays in your account. In other words, at the end of the year your money "rolls over." Any money you do not spend also earns interest.