This Medicare Mistake at Age 65 Could Haunt You for the Rest of Your Life

Remember when you were young and 65 seemed old? It probably never occurred to you that you'd still be spending time with friends, finding ways to have fun, and inevitably making a mistake or two.

Here's one mistake at age 65 that could cost you for the rest of your days.

Image source: Getty Images.

Age 65

Just imagine that you're about to turn 65. You're busy thinking about what you want to do for this milestone birthday.

Do you want to have dinner with family or go out with friends? Are you hoping to spend your 65th birthday skydiving or taking a once-in-a-lifetime trip? Or do you prefer a quiet night at home with a good book and a bottle of your favorite wine?

Whatever you're thinking about, it may not be the importance of signing up for Medicare. Yet failing to think about Medicare on and around your 65th birthday could be one of the most expensive mistakes you make.

The impact on Social Security

For most retirees, Medicare premiums are automatically deducted from their Social Security benefits. If you're still working or plan to maximize your Social Security benefits by waiting until age 70 to make a claim, paying for Medicare may be the last thing on your mind at age 65. But it shouldn't be.

You're required to sign up for Medicare Part B during one specific period -- from three months before your 65th birthday to three months after. Let's say you were born in April. In that case, you'd have from January through July to enroll in Medicare Part B, which helps cover doctor visits, outpatient care, home health services, mental health services, ambulance service, and durable medical equipment.

While most Americans pay nothing for Part A (hospitalization), the standard cost of Part B for most beneficiaries in 2026 is $202.90 a month. However, failure to enroll in Medicare during the initial seven-month window will trigger a permanent monthly late-enrollment penalty.

How the penalty works

As if navigating the high cost of healthcare in retirement isn't enough, you'll be stuck with a 10% penalty for every 12-month period you fail to enroll. For example, if the wires somehow get crossed and you believe that you don't have to enroll in Medicare until you're fully retired, you might easily delay enrollment for two or three years.

Failure to enroll three years past your enrollment window would result in a 30% penalty, meaning the Social Security Administration (SSA) would tack an extra 30% on your monthly premium for the rest of your life. So rather than paying $202.90 per month for coverage, you'd get stuck paying $263.77. That's extra money that you may need to pull from your savings or retirement account.

Exception to the rule

One exception to the rule is if you or your spouse still works for an employer that has 20 or more employees and creditable employer group health insurance. When that's the case, you can generally delay enrolling in Part B without penalty.

The last thing you want to do throughout retirement is pay more for Medicare than necessary. Simply signing up during the required seven-month window can prevent that from happening.

The Motley Fool has a disclosure policy.