Medicare 101: Key Dates, Deadlines, and What's New in 2026

If you’re turning 65 soon, or you just opened a thick envelope about next year’s plan, you’re probably asking the same question many of the families we work with ask: “What do I actually have to do, and when?”

That’s a fair question. Medicare comes with its own vocabulary, several enrollment windows, and late-enrollment penalties that can last for years, or even for life. The good news: once you see the calendar laid out, it’s very manageable. This guide covers the four parts of Medicare, every date that matters, what Medicare costs in 2026, how your income can raise your premiums, and the changes worth knowing about this year.

The four parts of Medicare, in plain English

There’s also Medigap (Medicare Supplement insurance). It pays some of the costs Original Medicare (Parts A and B) leaves behind, like deductibles and the 20% Part B coinsurance. You choose one of two paths: Original Medicare plus Medigap and Part D, or Medicare Advantage. Neither is right for everyone. The best fit depends on your doctors, your prescriptions, how much you travel, and how you feel about networks and costs that vary year to year.

The Medicare calendar: every date that matters

A quick example

The Medigap window is the one people miss

The 6-month Medigap Open Enrollment Period starts once you’re 65 and enrolled in Part B. It does not repeat each year. Outside that window, and outside a few protected situations, an insurer in most states can ask health questions and may charge more or decline coverage.⁴ If you start with Medicare Advantage and later want Original Medicare plus Medigap, you may not be able to get a Medigap policy on the same terms. That’s a good reason to choose your path carefully the first time.

Late penalties: why the dates matter

Missing a deadline doesn’t just delay coverage. It can raise your premiums for years, or even for life.⁵

• Part B: your premium can go up 10% for each full 12-month period you could have had Part B but didn’t sign up. The penalty is generally calculated as a percentage of the standard Part B premium for that year, so the dollar amount rises as the premium rises. You generally pay it for as long as you have Part B.
• Part D: if you go 63 days or more without Part D or other creditable drug coverage after your IEP, a penalty is added: 1% of the national base premium for each month you went without. It usually lasts as long as you have drug coverage.

Exceptions exist. You generally won’t owe a Part B penalty if you qualify for a Special Enrollment Period (for example, because you had coverage from current employment) or enroll in a Medicare Savings Program. You generally won’t owe a Part D penalty if you had creditable drug coverage or qualify for Extra Help.⁵

Still working at 65? Read this before you delay

Many people keep working past 65, and it’s often fine to delay Part B if you have group health coverage from current employment (yours or your spouse’s). You then get an 8-month Special Enrollment Period, which generally starts when your current employment or that employer coverage ends, whichever happens first.^2,6 Three details catch people off guard:

1. COBRA and retiree coverage don’t count. They are not coverage from current employment, so they don’t protect you from the Part B penalty, and COBRA does not extend your 8-month Special Enrollment Period.¹
2. Employer size can matter. At some smaller employers, Medicare pays first and the employer plan pays second. If that’s your situation, delaying Part B can leave large gaps in coverage. Ask your benefits office how its plan works with Medicare, and get the answer in writing.⁶
3. Health Savings Accounts. Once you’re enrolled in any part of Medicare, you can no longer contribute to an HSA. Part A enrollment can be backdated up to 6 months (but never earlier than the month you turned 65), so Medicare.gov suggests you and your employer stop HSA contributions 6 months before you retire or apply for Social Security, to avoid a tax penalty.^6,7

What Medicare costs in 2026

Sources: CMS 2026 Parts A & B fact sheet (Nov. 14, 2025); Medicare.gov “Medicare costs.”^8,9

That’s a 9.7% increase in the standard Part B premium from 2025. For most retirees, Part B is deducted directly from Social Security, so the increase takes part of each year’s cost-of-living raise.

IRMAA: how your income two years ago sets your premium today

Higher-income households pay more for Parts B and D through the Income-Related Monthly Adjustment Amount (IRMAA). Here’s the part that surprises most people: Social Security generally looks at your tax return from two years earlier. Your 2026 premiums are usually based on your 2024 modified adjusted gross income (MAGI).¹⁰

Source: CMS 2026 fact sheet; SSA “Medicare premiums.” Married-filing-separately brackets differ.^8,10

Why this matters for your plan

Because IRMAA is based on income, it’s partly plannable. Large Roth conversions, selling a business, exercising stock options, or realizing big capital gains can all push you into a higher tier two years later. Spreading income over several years, or timing it before your Medicare years begin, can reduce the impact.

And if your income drops because of a life-changing event, like retirement, reduced work hours, marriage, divorce, or a spouse’s death, you can ask Social Security to use your newer, lower income with Form SSA-44.¹⁰ Many people retire and never file it.

When we work with families approaching Medicare, IRMAA is one of the first things we map out, because it connects directly to their tax strategy and planning and their retirement income plan.

What’s new in 2026, and what’s coming for 2027

1. Part B premiums rose to $202.90

The standard premium went up from $185.00 to $202.90, and the deductible from $257 to $283.⁸ CMS released the 2026 figures on November 14, 2025. Watch for the 2027 numbers on a similar fall schedule.

2. The Part D out-of-pocket cap is $2,100

Under the redesigned Part D benefit, your out-of-pocket drug costs are capped at $2,100 for 2026. Once you reach the cap, covered Part D drugs cost you nothing more for the rest of the year.⁹ The cap is indexed each year. If you take expensive medications, the Medicare Prescription Payment Plan lets you spread those costs into monthly payments instead of paying large amounts early in the year. Ask your plan about it.

3. Negotiated drug prices have begun

The first Medicare-negotiated prices took effect in 2026. The next round, covering 15 more drugs including Ozempic, Rybelsus and Wegovy, diabetes drugs such as Janumet and Tradjenta, and inhalers such as Trelegy Ellipta and Breo Ellipta, takes effect January 1, 2027. A third round, including Part B drugs for the first time, is being negotiated in 2026 for 2028.¹¹ What you pay at the pharmacy still depends on your plan’s design, so check your 2027 plan details.

4. Arizona is one of six states in a new prior-authorization pilot

CMS’s WISeR Model began January 1, 2026, and the affected services became subject to review starting January 15, 2026. It adds a prior-authorization or pre-payment review step for a short list of services in Original Medicare in six states, including Arizona. Examples include certain skin substitutes, electrical nerve stimulator implants, and knee arthroscopy for osteoarthritis. CMS says the model doesn’t change what Medicare covers, excludes emergency and inpatient-only services, and runs through 2031. It doesn’t apply to Medicare Advantage.¹² If you’re in Original Medicare and one of these procedures is planned, ask your provider whether a prior-authorization request has been submitted.

5. 2027 plan ratings are out, and Open Enrollment starts October 15

CMS published the 2027 Medicare Advantage and Part D Star Ratings on Medicare Plan Finder on October 8, 2026. Stand-alone drug plans improved sharply. On an enrollment-weighted basis, about 22% of stand-alone drug plan enrollees are in contracts rated 4 stars or higher, up from 2% for 2026. That’s the share of enrollees, not the share of plans earning four stars.¹³ Plans change their premiums, drug lists, and networks every year, so a plan that fit well in 2026 may not fit in 2027. Read your Annual Notice of Change and compare plans before December 7.

Your Medicare checklist

You don’t have to do this alone. Free, unbiased plan counseling is available through your State Health Insurance Assistance Program (SHIP), and Medicare Plan Finder lets you compare plans side by side.³

Frequently asked questions

Related reading

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About the author

Justin Kauffman, CFP®, CEPA®, is President and Lead Wealth Advisor of Dominion Private Wealth in Goodyear, Arizona. He helps families and business owners across the Phoenix area design, build, and steward their entire financial lives, from retirement income and tax strategy to estate and legacy planning. Learn more about our team.

Sources

1. Medicare.gov, “When does Medicare coverage start?” medicare.gov/basics/get-started-with-medicare/sign-up/when-does-medicare-coverage-start (accessed Oct. 13, 2026).
2. Medicare.gov, Initial, General and Special Enrollment Periods (same page as source 1; accessed Oct. 13, 2026).
3. Medicare.gov, “Joining a health or drug plan.” medicare.gov/basics/get-started-with-medicare/get-more-coverage/joining-a-plan (accessed Oct. 13, 2026).
4. Medicare.gov, “Get ready to buy” (Medigap). medicare.gov/health-drug-plans/medigap/ready-to-buy (accessed Oct. 13, 2026).
5. Medicare.gov, “Avoid late enrollment penalties.” medicare.gov/basics/costs/medicare-costs/avoid-penalties (accessed Oct. 13, 2026).
6. Medicare.gov, “Working past 65.” medicare.gov/basics/get-started-with-medicare/medicare-basics/working-past-65 (accessed Oct. 13, 2026).
7. IRS, Publication 969 (2025), Health Savings Accounts and Other Tax-Favored Health Plans. irs.gov/publications/p969 (accessed Oct. 13, 2026).
8. CMS, “2026 Medicare Parts A & B Premiums and Deductibles” fact sheet, Nov. 14, 2025. cms.gov/newsroom/fact-sheets/2026-medicare-parts-b-premiums-deductibles
9. Medicare.gov, “Medicare costs: What you pay in 2026.” medicare.gov/basics/costs/medicare-costs (accessed Oct. 13, 2026).
10. Social Security Administration, “Premiums: Rules for Higher-Income Beneficiaries.” ssa.gov/benefits/medicare/medicare-premiums.html (accessed Oct. 13, 2026).
11. CMS, “Medicare Drug Price Negotiation Program: Selected Drugs and Negotiated Prices” (accessed Oct. 13, 2026).
12. CMS Innovation Center, “WISeR (Wasteful and Inappropriate Service Reduction) Model.” cms.gov/priorities/innovation/innovation-models/wiser (accessed Oct. 13, 2026). January 15, 2026 review start date per CMS model materials.
13. CMS, “2027 Medicare Advantage and Part D Star Ratings” fact sheet, Oct. 8, 2026.