10/28/2026
Turning 65 doesn't always mean you have to sign up for Medicare Part B. But whether you can safely wait depends on details most people never check.
If you're still working at 65 and covered by your employer's health plan, you may be able to delay Part B without a penalty. Three conditions decide it.
The coverage has to come from current employment, yours or your spouse's. COBRA and retiree plans don't qualify.
The employer has to have 20 or more employees. At a large employer, the group plan pays first and Medicare pays second. At a smaller employer, Medicare is generally expected to pay first. If you skip Part B there, the employer plan may refuse to pay claims Medicare would have covered, and a late enrollment penalty can start building from your 65th birthday.
You have to enroll on time when the job ends. You get eight months from the end of employment or employer coverage, whichever comes first.
One more detail catches people who are saving in a health savings account. Once you're enrolled in any part of Medicare, including premium-free Part A, you can no longer contribute to an HSA. And if you sign up for Part A after 65, it's usually backdated up to six months, though not earlier than the month you turned 65. Contributions made during those months can be treated as excess contributions, so the common approach is to stop HSA contributions six months before you enroll.
There's also a trap in how Part A starts. If you claim Social Security at 65 or later, you're enrolled in Part A automatically. That alone ends HSA eligibility, even if you're still on your employer's plan.
The right answer depends on your employer's size, what your plan costs compared to Medicare, and whether you or your spouse are still contributing to an HSA. All three are worth checking before your 65th birthday, not after.
Are you planning to keep working past 65?