Turning 65: The Month-by-Month Medicare Timeline That Protects Every Right You Have
Medicare is a timeline product: nearly every right you have — guaranteed issue, penalty avoidance, the six-month Medigap window — exists only inside specific date ranges. Miss one and the cost is permanent. This is the complete month-by-month schedule for the year you turn 65.
Months -3 to -1: the setup window
Your Initial Enrollment Period (IEP) opens three months before your 65th birthday month. This is when you enroll in Part A (always) and Part B (unless still covered by active employer insurance — verify the rules before delaying). Enrolling in month one of the IEP means coverage starts your birthday month with zero gap. Social Security processes enrollment online or by phone; benefits counselors are free through SHIP.
Month 0 (birthday month): Part B starts
If you enrolled early, Part B is live ($185/month standard 2025). The moment it starts, two clocks begin: your six-month Medigap Open Enrollment Period and, if applicable, employer-coverage coordination rules. If you are delaying Part B for employer coverage, confirm your employer plan is creditable and get it in writing — this document is your defense against future penalties.
Months 0 to +6: the Medigap golden window
During these six months, every carrier must sell you any plan at your age price with no health questions. This is the only period in most people’s lives when Medigap is fully accessible. The sequence that works: enroll in Part B in month zero, shortlist Plan G and Plan N quotes within a fortnight, verify five-year increase histories, and apply in month one or two.
Months 0 to +8: the Part D and penalty clocks
You have until three months after Part B starts to pick a Part D drug plan without a late-enrollment penalty — a lifetime 1%-per-month surcharge on future premiums. Even people on zero medications should buy the cheapest credible plan ($7–15/month) to keep the clock off. The same three-month tail governs Medicare Advantage enrollment if you chose that path instead.
| Window | Duration | Miss it and… |
|---|---|---|
| IEP (Part A/B) | 7 months around 65 | Lifetime Part B penalty: 10%/full year late |
| Medigap OEP | 6 months from Part B | Underwriting for life (most states) |
| Part D IEP | 7 months around 65 | Lifetime 1%-per-month premium surcharge |
Month +7 onward: the maintenance years
After the windows close, your calendar shifts to annual rhythms: October 15–December 7 re-shop Part D (and MA plans) against the next year’s formularies; check whether your state grants birthday-rule or annual GI switching rights for Medigap; and keep every creditable-coverage notice filed. The people who get hurt by Medicare are almost always the people who treated a deadline product like a set-and-forget product.
Related: all enrollment windows, OEP deep dive, Part D penalty mechanics.