Medicare
The seven months that decide what Medicare costs you for life
Miss your enrollment window and Medicare does not fine you once — it raises your premium permanently. The calendar below, plus the two situations where the usual advice is wrong.
Medicare has a reputation for being complicated. Most of that complication comes down to one thing: dates. Miss the right window and Medicare does not fine you once and move on — it adds a surcharge to your premium and keeps it there for as long as you have the coverage.
That is the part people find out too late. So let's take the calendar in the order it actually matters.
Your first window is seven months long
Your Initial Enrollment Period runs for seven months: the three months before the month you turn 65, your birthday month itself, and the three months after. That is the whole window.
When your coverage starts depends on where in that window you file. Part A generally starts the month you turn 65 — and if your birthday falls on the first of the month, it starts the month before. For Part B, filing early matters: sign up before your birthday month and coverage begins the month you turn 65; sign up during or after it and coverage starts the following month. Coverage always begins on the first of a month.
The practical lesson is simple. Filing in the first three months costs you nothing and avoids a gap. Filing in the last three costs you a delay you did not need.
What the late penalties actually are
This is where the numbers stop being abstract.
Part B. You pay an extra 10% for each full 12-month period you could have had Part B and did not. It is not a one-time charge. It rides on your monthly premium for as long as you have Part B. In 2026 the standard premium is $202.90 a month, so a two-year delay means roughly $40 extra every month — about $487 a year, forever, on top of the premium itself.
Part D. The drug-coverage penalty works per month: 1% of the national base beneficiary premium for every month you went without creditable drug coverage. That base was $38.99 in 2026. Fourteen months without coverage is a 14% penalty, and it follows you even if you later switch plans.
Both amounts move a little each year, because both are tied to figures that reset annually. The rules that create them do not move.
When delaying is genuinely fine
Blanket advice falls apart here. If you are still working at 65 and covered by an employer plan through active employment, you can usually delay Part B without any penalty, and pick it up later through a Special Enrollment Period. For many people that is the right financial call.
The traps are in the details:
- The exemption comes from active employment coverage. COBRA and retiree coverage are not the same thing, and relying on them is one of the most expensive mistakes in this whole subject.
- Employer size matters for whether Medicare or the employer plan pays first.
- If you have a Health Savings Account, contributions have to stop before Part A begins, and Part A can be backdated — so the timing needs planning, not guessing.
None of this is guesswork territory. Ask your HR department for written confirmation that your coverage counts as creditable, and keep it.
The two dates worth putting in your calendar
Once you are enrolled, two recurring windows matter:
- October 15 – December 7. The Annual Enrollment Period: you can change your Medicare Advantage or Part D plan for the coming year. Plans change their formularies and networks annually, which is why "it worked last year" is not a reason to skip the review.
- January 1 – March 31. If you are in a Medicare Advantage plan, you get one chance to switch to a different Advantage plan or return to Original Medicare.
One more window nobody mentions
If you are considering a Medigap policy, there is a separate six-month window that starts the first month you are both 65 or older and enrolled in Part B. During it, insurers must sell you any Medigap policy they offer in your state, cannot refuse you for health reasons, and cannot charge you more because of your medical history.
After those six months, federal law no longer guarantees any of that. Companies can require medical underwriting, and they can decline. Some states add protections — Texas rules are worth checking for your specific case.
That window is short, it is easy to miss while you are busy comparing Medicare plans, and unlike the others it does not come back around every year.
If you are approaching 65, or still working and unsure whether to delay, this is exactly the kind of thing worth a fifteen-minute conversation. I do not charge for it, and the answer usually depends on two or three specifics about your situation that no article can guess.
Frequently asked questions
Can I sign up for Medicare before I turn 65?
Yes. Your Initial Enrollment Period opens three months before the month you turn 65, and filing in those first three months is the cleanest option — your Part B coverage then starts the month you turn 65, with no gap.
What happens if I miss my Initial Enrollment Period?
You can still enroll later, but Part B adds 10% to your premium for each full 12-month period you could have had it and did not, and that surcharge stays for as long as you have Part B. The Part D penalty works similarly, at 1% per month without creditable drug coverage.
I am still working at 65. Do I have to take Part B?
Usually not, if your coverage comes from active employment — you can delay without penalty and enroll later through a Special Enrollment Period. The exemption does not extend to COBRA or retiree coverage, so get written confirmation from HR that your plan counts as creditable.
Is there a deadline for buying a Medigap policy?
There is a separate six-month window that begins the first month you are both 65 or older and enrolled in Part B. During it insurers cannot refuse you or charge more because of your health. After it, federal law no longer guarantees that.