Employees who have enjoyed the benefit of health savings accounts (HSAs) may be in for a taxing surprise when they enroll in Medicare. That’s because Medicare enrollment disqualifies someone from contributing to an HSA.

Working employees may sign up for premium free Medicare Part A when they are first eligible for coverage at age 65. Signing up for Part A or signing up for social security, which triggers enrollment in Part A, requires a person to cease making HSA contributions. A person who signs up for social security is automatically signed up for Medicare Part A.

By claiming social security benefits after age 65, an automatic retroactive coverage period for Part A is triggered. The retroactive period is limited to six months or the entitlement date for Medicare, whichever is shorter. HSA contributions made during this Part A retroactive period may result in an IRS penalty.

Working aged employees or spouses can delay enrollment in Medicare Parts A and B if they are enrolled in an employer group health plan. Before considering this option, it’s important to understand whether the employer plan will assume coordination with Medicare benefits. If Medicare is the primary payer, the employee could have to pay the expenses that Medicare would have paid out of their own pocket.

Employees should discuss their Medicare and HSA options with their benefits advisor and accountant well in advance of reaching age 65.