Most people should enroll around age 65 during their seven-month Initial Enrollment Period. You may be able to delay Part B without a penalty if you have qualifying coverage from your or your spouse's current employment.
Most people should enroll in Medicare during the seven-month period around their 65th birthday. Your timing may differ if you are enrolled automatically or have insurance through your own or your spouse’s current job.
Part A helps cover inpatient hospital care. Part B helps cover doctor visits and outpatient care.
Before delaying Part B, answer two questions: Can you enroll later without a penalty, and will your present insurance pay your bills while you wait? COBRA, retiree insurance, and Marketplace coverage generally do not let you delay Part B without a penalty under the current-employment rules. Insurance from a current job with a small employer may let you enroll later without a penalty, even if Medicare needs to pay your bills first.
Your Initial Enrollment Period
Your Initial Enrollment Period generally lasts seven months:
- Three months before the month you turn 65
- The month you turn 65
- Three months after your birthday month
For Part B to start when you turn 65, sign up before your birthday month. If you enroll during your birthday month or the next three months, coverage generally begins the following month.
Birthdays on the 1st work differently. Your enrollment window opens four months before your birthday month and closes two months after it. You can also start Part B one month earlier. For example, if you turn 65 on July 1, enroll by May 31 for coverage to begin June 1.
Do You Need to Sign Up?
You usually receive Part A and Part B automatically if you started receiving Social Security or Railroad Retirement Board benefits at least four months before you turn 65. Medicare will send enrollment information and your card.
If you are not receiving those benefits, you usually need to enroll through Social Security. The official Medicare sign-up tool provides instructions based on your situation.
Can You Delay Part B While Working?
You may be able to delay Part B without a late penalty if you or your spouse is actively working and you are covered by that current employer's group health plan. Ask the benefits administrator which insurer pays first and whether the employer plan reduces payment if you do not enroll in Medicare. Also ask Social Security whether you can delay Part B without a penalty.
When the employment or job-based coverage ends, you may receive an eight-month Special Enrollment Period for Part B. That window generally starts when employment or the coverage ends, whichever comes first.
Do not treat COBRA as current-employment coverage. Taking COBRA does not extend the eight-month Part B enrollment window.
What About Part A?
Many people take premium-free Part A at 65 even if they delay Part B. If you or your employer puts money into a Health Savings Account (HSA), plan carefully. When you enroll after 65, premium-free Part A can start up to six months before you apply, but not before the month you became eligible. Your HSA contribution limit is zero for months covered by Medicare, including any months before you applied.
Before applying for Medicare or Social Security after 65, use Medicare’s working-past-65 guidance to plan when both you and your employer will stop HSA contributions. Check the Part A start date when deciding when to stop adding money. Get tax help if HSA contributions overlap Medicare coverage. You can still spend money already in the account on qualified medical expenses.
When Should You Add Drug Coverage?
Enroll in Part D when first eligible unless you have other prescription coverage that is creditable, meaning it is expected to pay at least as much as standard Medicare drug coverage. After your Initial Enrollment Period ends, going 63 consecutive days or more without Part D or creditable drug coverage can trigger a late-enrollment penalty later.
Ask your current plan for its annual creditable-coverage notice and keep it with your records.
A Practical Timeline
Example: retiring after 65 with employer coverage through November 30, 2026. Arrange Part B before that coverage ends and request a December 1 start if eligible. Confirm the effective date with Social Security. The eight-month Special Enrollment Period gives you time to sign up. It does not provide health insurance while you wait.
Coordinate three separate decisions:
- A and B: Use the enrollment period that applies to you and confirm both start dates.
- Drug coverage: Check the deadline after creditable drug coverage ends; the Part D window is not the eight-month Part B window.
- Medigap: Original Medicare means Parts A and B. Medigap is supplemental insurance that helps pay some costs Original Medicare leaves to you. If you choose Original Medicare, check the six-month window tied to age 65 or older and Part B before it expires.
Keep the old coverage until you have confirmed the new start dates. Ask the employer how ending your enrollment affects anyone else covered by the same plan.
Medicare policy sources last checked: October 8, 2026.