Most Medicare guidance assumes you're retiring around 65. If you're not, working full time with coverage through your job or a spouse's, the usual advice doesn't quite fit, and the stakes for getting it right are real: delay the wrong part, and you could face a lifetime penalty. Delay the right part, and you save money without losing coverage.
Part A: usually, sign up anyway
Part A covers hospital stays, and for most people it's premium-free because of years worked and paid into Medicare through payroll taxes. There's rarely a reason to delay it, even if you're still working, unless you're contributing to a Health Savings Account, which Part A enrollment can affect. That's a specific situation worth asking about directly.
Part B: this is the one that matters
Part B carries a monthly premium, and it's the part people most often want to delay while working. Whether you safely can depends almost entirely on the size of your employer.
- 20 or more employees: your employer plan is usually primary, and you can typically delay Part B without a penalty, as long as the coverage counts as creditable
- Fewer than 20 employees: Medicare usually becomes primary at 65 regardless of your employer coverage, and delaying Part B can leave real gaps
- Retiree coverage or COBRA: neither generally counts as active employment, and delaying Part B based on either one is a common, costly mistake
The Special Enrollment Period that covers you later
If you do delay Part B correctly while on qualifying employer coverage, you get a Special Enrollment Period when that employment or coverage ends, eight months to sign up for Part B without a penalty. Miss that window, and you're back to waiting for the General Enrollment Period with a penalty attached.
What about your spouse?
If your spouse is under 65 and covered under your employer plan, your decision affects them too. Losing that coverage because you switched to Medicare can leave a younger spouse needing separate coverage of their own before they're Medicare-eligible. That's a real cost to weigh alongside the Part B decision, not an afterthought.
Don't rely on what worked for a coworker
Employer size, plan type, and whether coverage is truly "creditable" all change the answer, so what was correct for someone else at a different company isn't automatically correct for you. This is one of the few Medicare decisions genuinely worth confirming in writing before you act on it.
Social Security's guidance on Medicare while working covers the rules in more detail at ssa.gov/medicare. If you'd rather have someone check your specific employer coverage against the rules, bring your plan details to a free review and we'll tell you plainly whether delaying is safe for you.