Medicare Enrollment Guide: Turning 65

The Initial Enrollment Period (IEP) is a 7-month window during which you can first enroll in Medicare. It begins 3 months before the month you turn 65, includes your birth month, and ends 3 months after. For example, if you turn 65 in July, your IEP runs April 1 through October 31. When you enroll during this window matters for when coverage begins: enrolling in the 3 months before your birth month means coverage starts on the 1st of your birth month. Enrolling during your birth month or in the 3 months after results in a delayed coverage start — up to 3 months after you sign up. To avoid any gap in coverage, enroll in the 3 months before your birth month whenever possible.

If you do not enroll in Medicare Part B when you are first eligible and do not have qualifying employer coverage (called creditable coverage), you face a permanent late enrollment penalty: 10% added to the standard Part B premium for every 12-month period you were eligible but not enrolled. This penalty lasts for as long as you have Part B — it never goes away. For example: if you delay Part B enrollment for 3 years without creditable coverage, your Part B premium is permanently 30% higher. In 2026, the standard Part B premium is $202.90/month. A 30% penalty would add roughly $60/month — $720/year — to your Medicare cost for life. The same penalty structure applies to Part D drug coverage, calculated at 1% per month of delay.

If you are still actively employed at 65 and covered under a group health plan from your employer (or your spouse's employer), you generally have the right to delay Medicare enrollment without penalty — but only if the employer plan qualifies as 'creditable coverage.' The key factors are: (1) the employer must have 20 or more employees; (2) the employer plan must be primary (paying before Medicare); and (3) you must have active employment coverage, not retiree coverage. COBRA coverage and retiree coverage do NOT qualify as creditable coverage for delaying Medicare. If your employer has fewer than 20 employees, Medicare becomes primary and you should still enroll. Always get a letter from your employer HR department confirming your coverage is creditable before deciding to delay.

Medigap (Medicare Supplement) insurance has a federally guaranteed open enrollment window: a 6-month period that starts the month you are both age 65 or older AND enrolled in Medicare Part B. During this window, insurers must sell you any Medigap plan they offer at the best available rate — regardless of your health history. This is guaranteed issue, meaning you cannot be turned down or charged more due to pre-existing conditions. Once this window closes, you can still apply for Medigap outside open enrollment, but insurers in most states can use medical underwriting — meaning they can decline your application or charge significantly higher premiums based on your health. This makes the initial 6-month window extraordinarily valuable. If you think you may want a Medigap plan someday, strongly consider enrolling during this guaranteed window.

IRMAA (Income-Related Monthly Adjustment Amount) is an additional surcharge added to Medicare Part B and Part D premiums for higher-income beneficiaries. It is based on your modified adjusted gross income (MAGI) from two years prior — so your 2026 Medicare premiums are based on your 2024 tax return. In 2026, IRMAA surcharges begin for individuals with 2024 MAGI above $109,000 (based on 2024 MAGI) and for married couples filing jointly above $218,000 (based on 2024 MAGI). The surcharge tiers go up significantly for very high earners. If your income has dropped significantly since the year being used (e.g., due to retirement), you can appeal IRMAA using Form SSA-44 (Medicare Income-Related Monthly Adjustment Amount) to use more recent income figures.