Medicare Planning for High Earners: 2026 Enrollment, Plan Choice & Cost Guide

For the $1M–$5M investor approaching 65, Medicare is not a one-size-fits-all enrollment. IRMAA surcharges mean you pay more than most. Choosing Medigap vs. Medicare Advantage has a different calculus when you can self-insure surprises. And enrolling at the wrong time — or while still contributing to an HSA — creates penalties and tax hits that follow you for life. This guide walks through every decision point, with an interactive cost estimator.

Medicare's four parts — what you're actually buying

Most people with 40+ quarters of work history pay $0 for Part A and add Part B (required to get any supplemental coverage). From there, you choose between Original Medicare + Medigap + standalone Part D, or a Medicare Advantage plan that bundles everything.

When to enroll: the windows that matter

Initial Enrollment Period (IEP). You have a 7-month window: 3 months before your 65th birth month, your birth month itself, and 3 months after. Enrolling in the first 3 months means coverage begins the 1st of your birth month. Enrolling later delays coverage start. Most people should enroll in the 3 months before turning 65 to avoid a gap.

Special Enrollment Period (SEP). If you're still working at 65 and covered by a qualifying employer plan (employer with 20+ employees), you can delay Medicare without penalty. You get an SEP lasting 8 months after losing that coverage — but you must enroll within that window or the late enrollment penalty kicks in permanently.

General Enrollment Period (GEP). If you miss both the IEP and SEP, you can enroll January–March each year, with coverage starting July 1. The late enrollment penalty also applies.

Still working at 65? How employer coverage affects the math

If your employer has 20+ employees and you're actively employed, your group plan is primary and Medicare is secondary. You can delay Part B (and the premium) without penalty as long as coverage continues.

Key rules:

• COBRA does not count as active employer coverage for purposes of avoiding the late enrollment penalty. If you retire and take COBRA, enroll in Medicare — the clock starts ticking from when your active employment ended, not when COBRA runs out.
• Retiree coverage also does not count. Former-employer retiree health plans are not "active" coverage under Medicare's rules. Same result: enroll or face a penalty.
• Spouse's employer plan can delay your Medicare if the employer has 20+ employees and you're enrolled as a dependent on an active employee's plan.
• Medicare eligibility doesn't force enrollment. Turning 65 triggers eligibility, not obligation — as long as you have qualifying coverage. But confirm your plan is qualifying with your HR department; some executive medical plans have wrinkles.

The HSA trap most people miss

If you're enrolled in a high-deductible health plan (HDHP) and contributing to an HSA, be aware of this specific rule: enrolling in Medicare Part A triggers a 6-month retroactive coverage period. Medicare Part A enrollment reaches back 6 months from the date you apply (but no earlier than your 65th birthday).

Any HSA contributions made during that retroactive 6-month window become excess contributions — taxed as income plus a 6% excise penalty. If you plan to enroll in Medicare at 65, stop HSA contributions at least 6 months before your Part A start date. If you plan to delay Medicare past 65 to keep contributing to an HSA, do not claim Social Security before age 65 — Social Security enrollment automatically triggers Part A.

Medigap Plan G vs. Medicare Advantage — the high-earner's choice

Once enrolled in Parts A and B, you have two paths. This decision is permanent in a meaningful sense: switching from Medicare Advantage back to Medigap later requires medical underwriting in most states, and you may be denied or charged more based on health. The Medigap Open Enrollment Period (the 6 months after first enrolling in Part B at age 65+) is your one guaranteed no-underwriting window.

The high-earner case for Medigap Plan G: At $1M–$5M in assets, the extra $100–$200/month for Plan G buys predictability and unlimited provider access. You can afford the premium; you cannot easily predict which year you'll need high-cost care — and a year with serious illness can consume an MA plan's full $9,350 out-of-pocket max while Medigap costs you almost nothing beyond the deductible. Frequent travelers and those who split time between states (snowbirds) especially benefit from Plan G's nationwide coverage.

When MA can make sense: If you live in an area with a high-rated integrated MA plan (Kaiser Permanente regions, SCAN in California), are in excellent health and comfortable with network restrictions, and plan to re-evaluate coverage each year — MA can work well. Just know the exit door from MA back to comprehensive Medigap narrows with age and health.

Part D — don't skip it, even if you take no prescriptions

Part D late enrollment penalty: for each month you go without creditable drug coverage, you owe roughly 1% of the national base beneficiary premium ($38.99 in 2026) per month — permanently.³ Twelve months without coverage adds ~$4.68/year; but the bigger risk is being uninsured when you actually need a prescription drug. Enroll in a low-cost Part D plan when you first become eligible, even if you're healthy.

If you choose Medigap, pick a standalone Part D plan alongside it. If you choose Medicare Advantage with drug coverage (MA-PD), your drug coverage is bundled in. Either way, you still pay Part D IRMAA if your income exceeds the threshold.

2026 Medicare annual cost estimator

Enter your income (2024 MAGI, since 2026 Medicare costs are based on your 2024 return), filing status, how many people on Medicare, and your plan type. The calculator shows your estimated total annual Medicare spending.

Calculator uses 2026 IRMAA thresholds and premiums per CMS fact sheet¹ and Part D base per CMS.² Medicare Advantage out-of-pocket costs are not included — actual MA costs depend heavily on utilization. Medigap premiums are user-entered estimates; actual premiums vary by age, state, carrier, and tobacco status. Part A premium assumed $0 (40+ work quarters).

5 Medicare planning actions for the $1M–$5M investor

1. Set a 65th-birthday reminder 9 months out. Start the process 3 months before your IEP opens so you have time to compare plans without rushing. Your IEP opens 3 months before your birth month.
2. If still working, verify your employer plan is qualifying. Confirm with HR that the plan is from an employer with 20+ employees. Executive carve-outs and retiree plans don't satisfy the exemption.
3. Stop HSA contributions 6 months before Medicare Part A enrollment. The retroactive 6-month rule is the most common expensive surprise for late-career HSA users. Stopping contributions 6 months early avoids it entirely.
4. Buy Medigap Plan G during your Open Enrollment Period. The 6-month window after first enrolling in Part B at 65+ is the only time you're guaranteed acceptance regardless of health. Plan G covers essentially everything after the $283 annual Part B deductible. You cannot easily get comprehensive Medigap coverage later if your health changes.
5. Manage MAGI to stay below IRMAA thresholds. Roth conversions, large capital gain events, and RMDs in the same year can spike your income into a higher IRMAA tier — two years later. Model the 2-year lookback into your tax planning. If a qualifying life event drops your income, file Form SSA-44 to request a premium reduction. See our IRMAA planning guide for the full playbook.

How a fee-only advisor helps with Medicare planning

Medicare decisions interact with Roth conversion strategy (converting before 65 to reduce IRMAA-triggering income later), Social Security timing (delaying SS to 70 while managing ACA MAGI before Medicare; see our Social Security guide), RMD sequencing, and HSA investment strategy. These pieces move together. A fee-only advisor who works with $1M–$5M clients will model these interactions — not just hand you a Medicare checklist.