Turning 65 does not force a Medicare Part B enrollment on someone who is still working and covered by a group health plan through an employer. Medicare.gov’s rules give that person an eight-month window to sign up for Part B without penalty once the job or the group coverage ends, whichever happens first. Electing COBRA afterward does not pause or reset that clock.
Two things the 8-month window doesn’t cover: Signing up for Part B on time avoids the penalty, but it doesn’t sort the 51 state Medicare cost-help packs or set up a medication and cost tracker. The Medicare Cost & Coverage Protection Kit does both. Sort the state cost-help programs for a first Medicare bill →
The Eight-Month Clock
Medicare’s page on working past 65 states that once employment or the underlying group health coverage ends, whichever happens first, a Special Enrollment Period opens and runs for eight months. Signing up for Part B anywhere inside that window carries no late penalty, even though the standard enrollment periods most new Medicare beneficiaries rely on have already long closed by the time someone works past 65.
The Seven-Month Window It Replaces
For most people, Medicare enrollment runs on a different schedule entirely. The Centers for Medicare & Medicaid Services describes an Initial Enrollment Period that lasts seven months, starting three months before the month someone turns 65, including that birthday month, and ending three months after it. Someone still working with employer coverage at 65 can let that seven-month window pass without penalty, because the eight-month Special Enrollment Period described above exists specifically to pick up where the standard window left off, once work or the group plan actually ends.
Who The Eight Months Is For
The Special Enrollment Period exists for people who delayed Part B specifically because they were still working past 65 and covered by a group health plan tied to that job, rather than for anyone who simply forgot to sign up at 65. Original Medicare’s Part A, which most people get premium-free based on work history, typically starts on its own regardless of employment, so the eight-month clock at issue here is almost always a Part B question: the piece of Medicare that carries a monthly premium and the one most likely to be delayed deliberately while employer coverage is still in place.
Why COBRA Doesn’t Reset It
Medicare’s page on when Medicare coverage starts is direct about the one exception that trips people up: COBRA continuation coverage is not treated as group health plan coverage for this purpose, so electing COBRA after a job ends does not pause or restart the eight-month clock. The window keeps running from the date the job or the underlying group coverage actually ended, regardless of how many months of COBRA payments follow.
What Missing the Window Costs
Medicare’s page on avoiding late enrollment penalties puts a number on what happens next: Part B carries a 10 percent penalty added to the premium for every 12-month period someone was eligible but did not sign up, and that penalty typically lasts for as long as the person keeps Part B. Applied to the 2026 standard Part B premium of $202.90 a month, one missed year adds a permanent surcharge on top of every future bill, and two missed years would double that surcharge, compounding for as long as the person carries Part B at all. That is exactly the outcome the eight-month window is built to prevent for someone whose only lapse was still being on the job past 65, and it is why the distinction between “still covered by an employer plan” and “simply late” carries a real, ongoing dollar cost rather than a one-time fee.
A Different Question: When Coverage Can Start
The same coverage-start page also addresses a separate decision some people face: someone who signs up for Part B while still employed, rather than waiting for the eight-month window to open, can ask Medicare to delay the actual Part B start date by up to three months so coverage does not begin before it is needed. That option exists specifically for people enrolling while still working, and it is unrelated to the eight-month penalty-free window that opens only after work or group coverage has actually ended, since the two rules solve different scheduling problems for two different groups of applicants.
One Rule, Two Deadlines Inside It
Medicare’s guidance on working past 65 and its guidance on when coverage starts describe the same eight-month period from two angles: one names the enrollment deadline, the other names how quickly the resulting coverage can begin once someone applies. Both agree that COBRA is not counted as employer coverage for measuring that eight months, so a worker’s last day on the group health plan, not the date of a final COBRA payment, is the date that actually matters. Someone who applies early in the eight months, while still receiving COBRA payments from a former employer, does not get penalized for that overlap either, since the clock only cares about when the underlying group coverage from actual employment ended, not about anything paid afterward to extend it temporarily.
After Part B Starts, the Cost Questions Begin
Signing up for Part B inside the eight-month window avoids a penalty that would otherwise attach to the premium for as long as coverage lasts. It does not address what that premium and its deductible will run in a specific state, or where state-level programs that help pay Part B premiums can be found.
The Medicare Cost & Coverage Protection Kit collects 51 state Medicare cost-help packs alongside a medication and cost tracker, so a new Part B enrollee can see what help exists locally and keep costs organized from the first bill.
Look up the cost-help programs for the enrollment state in The Medicare Cost & Coverage Protection Kit.
This article was drafted with AI assistance and reviewed by a human editor prior to publication.
