Part D changed more between 2024 and 2026 than in the previous fifteen years, and the change is structural rather than cosmetic. For the first time there is a hard ceiling on what an enrollee can pay out of pocket for covered drugs in a year. In 2026 that ceiling is $2,100. Before 2025 there was none.
That single fact reorders the decision. The old question was how to survive the coverage gap. The current question is narrower: which plan’s formulary covers the specific drugs somebody takes, and what does the late-enrollment penalty cost if they skip it.
The 2026 standard benefit, in three phases
Every Part D plan has to be worth at least as much as a benefit design CMS writes each year. Most plans improve on it. That design is the floor, and it is the yardstick the rest of this article uses.
| Phase | What the enrollee pays | Where it ends in 2026 |
|---|---|---|
| Annual deductible | 100 percent of gross covered drug costs | Once $615 is met. Plans may set a lower deductible or none at all. |
| Initial coverage | 25 percent coinsurance on covered drugs | Once out-of-pocket spending reaches $2,100 |
| Catastrophic | Nothing further for covered Part D drugs | Runs to the end of the calendar year |
The $2,100 threshold is the 2025 cap of $2,000 indexed to growth in average Part D drug spending, so it will move again. Two limits on the comfort it offers are worth stating plainly. It applies to covered Part D drugs only, so a drug the plan does not list does not count toward it. And it is a calendar-year figure that resets every January, which matters for anyone whose expensive course of treatment straddles a year boundary.
One practical addition since 2025 is the Medicare Prescription Payment Plan, which lets an enrollee spread out-of-pocket drug costs across the calendar year in monthly instalments rather than paying them at the pharmacy counter. It does not reduce the total. It changes when it is due, which matters most for somebody who would otherwise hit a large share of that $2,100 in January.
The late-enrollment penalty is permanent, and that is the part people miss
Skipping Part D when first eligible is not a free decision deferred. CMS states the penalty applies where there is a continuous period of 63 days or more, after the end of the initial enrollment period, during which somebody was eligible for Part D but was not enrolled and was not covered by any creditable prescription drug coverage.
The penalty is calculated as a percentage of the national base beneficiary premium for each full month without coverage, added to the plan premium, and it generally continues for as long as somebody has Part D. It is not a one-time fee and it does not fall away after a few years. Because the base premium is recalculated annually, the penalty amount moves with it.
The arithmetic that matters is not this year’s premium against this year’s prescriptions. It is a modest premium now against a permanent surcharge later, for somebody who will almost certainly need drug coverage at some point in a retirement that may run thirty years.
Creditable coverage, and a 2026 rule change worth knowing
Somebody with drug coverage from an employer, a union, or certain other sources may delay Part D without penalty, provided that coverage is creditable. CMS defines creditable as having an actuarial value that equals or exceeds the value of defined standard Part D coverage.
Here is the part that changed. Because the IRA made the Part D benefit richer, CMS found the long-standing simplified test no longer reflected actuarial equivalence, and developed a revised one. Under the revised methodology a group health plan must be designed to pay at least 72 percent of participants’ prescription drug expenses, against 60 percent under the existing method. For 2026 only, non-RDS group health plans may use either test.
The consumer consequence is concrete. A plan that was comfortably creditable under the old 60 percent test may not clear 72 percent, and employers get to choose which test to apply in 2026. So the annual creditable-coverage notice from an employer plan is worth reading this year rather than filing, and worth keeping. That notice is the evidence that avoids a penalty later.
The income surcharge on top
Part D premiums have been income-related since 2011. CMS reports roughly 8 percent of Part D enrollees pay an income-related monthly adjustment amount in addition to the plan premium. The 2026 amounts use the same income brackets as Part B.
| 2026 modified AGI, individual | 2026 modified AGI, joint | Monthly amount added to the plan premium |
|---|---|---|
| $109,000 or less | $218,000 or less | $0.00 |
| Over $109,000 up to $137,000 | Over $218,000 up to $274,000 | $14.50 |
| Over $137,000 up to $171,000 | Over $274,000 up to $342,000 | $37.50 |
| Over $171,000 up to $205,000 | Over $342,000 up to $410,000 | $60.40 |
| Over $205,000 and under $500,000 | Over $410,000 and under $750,000 | $83.30 |
| $500,000 or more | $750,000 or more | $91.00 |
CMS notes that roughly two-thirds of beneficiaries pay Part D premiums directly to the plan while the rest have them deducted from Social Security. The income-related amount is handled separately: it is deducted from the Social Security payment or billed by Medicare directly, never collected by the plan.
Which drugs Part D does not pay for
Some drugs are covered under Part B rather than Part D, and the split is about how a drug is administered rather than what it treats. Drugs given in a physician’s office, infused, or supplied with durable medical equipment generally fall under Part B and its 20 percent coinsurance. Drugs picked up at a pharmacy generally fall under Part D. The same molecule can land on either side depending on the setting.
That distinction matters for the $2,100 ceiling, because only Part D spending counts toward it. A course of treatment delivered in an infusion suite runs against Part B coinsurance, which has no annual limit under Original Medicare at all. Anybody comparing plans on drug cost alone is looking at one of two pipes.
Separately, each plan’s formulary tiers its covered drugs, and plans use utilisation management: prior authorisation, step therapy, and quantity limits. A drug can be on the formulary and still require the plan’s permission before it is filled. When checking a plan, the question is not only whether a drug appears but on which tier and with what conditions attached.
Why this article does not name a best plan
Because there is no such thing, and because the sites that publish one are usually paid per enrollment. Part D plans differ by county, change every year, and are decided almost entirely by formulary rather than by premium. Two plans with the same monthly cost can differ by thousands of dollars a year for the same person depending on which tier each assigns to one drug.
The method that works is unglamorous. Write down every prescription with its dose. Enter them into the plan finder at medicare.gov, which prices the actual drug list against every plan available in the ZIP code and includes the pharmacy. Then check the annual notice of change each autumn, because the formulary that made a plan right this year may not next year. State Health Insurance Assistance Programs give this help free and take no commission.
Questions readers actually ask
Do I need Part D if I take no prescriptions?
Taking nothing today does not exempt anybody from the penalty. CMS applies it after 63 or more continuous days without creditable coverage following the initial enrollment period, and it is added to the premium for as long as somebody holds Part D. A low-premium plan held from the start is the usual way people avoid a permanent surcharge on coverage they will very likely need later.
What actually counts as creditable coverage?
Coverage whose actuarial value equals or exceeds defined standard Part D coverage. For 2026 a non-RDS group health plan may be tested either way: at least 60 percent of participants’ drug expenses under the existing simplified method, or at least 72 percent under the revised one CMS developed after the IRA enriched the Part D benefit. Ask the plan administrator in writing and keep the annual notice.
Does the $2,100 cap cover everything I spend at the pharmacy?
No. It applies to covered Part D drugs under the plan. Spending on a drug the plan does not cover does not count toward the threshold, which is why the formulary matters more than the premium. The cap also resets each January.
Can I keep Part D and an employer plan at the same time?
Sometimes, but enrolling in Part D can end an employer or retiree drug benefit for the household in some plan designs, and that can affect a spouse as well. Confirm with the plan administrator before enrolling rather than after. If the employer coverage is creditable, delaying Part D carries no penalty.
Sources
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Every figure in this article traces to a government record or to a named independent, non-commercial research body. We do not cite insurance marketplaces or affiliate comparison sites for data.
- Centers for Medicare & Medicaid Services Final CY 2026 Part D Redesign Program Instructions Published 2025-04-07Supports: 2026 defined standard benefit: deductible $615 with the enrollee paying 100 percent of gross covered drug costs until met; initial coverage at 25 percent enrollee coinsurance; catastrophic phase with no enrollee cost sharing; CY2026 annual out-of-pocket threshold $2,100, being the 2025 cap of $2,000 adjusted by the annual percentage increase in average Part D drug expenditures; late enrollment penalty arises after a continuous period of 63 days or more following the initial enrollment period without Part D and without creditable coverage; creditable coverage must have actuarial value equal to or exceeding defined standard Part D coverage; CMS developed a revised simplified determination methodology requiring group health plan coverage to pay at least 72 percent of participants prescription drug expenses against 60 percent under the existing methodology, and for CY2026 only non-RDS group health plans may use either.
- Centers for Medicare & Medicaid Services 2026 Medicare Parts A & B Premiums and Deductibles; 2026 Medicare Part D Income-Related Monthly Adjustment Amounts Published 2025-11-14Supports: Part D premiums have been income-related since 2011 and approximately 8 percent of Part D enrollees pay an income-related monthly adjustment amount; 2026 Part D IRMAA amounts of $0.00, $14.50, $37.50, $60.40, $83.30 and $91.00 across brackets beginning above $109,000 individual and $218,000 joint; roughly two-thirds of beneficiaries pay Part D premiums directly to the plan while the remainder have them deducted from Social Security, and the income-related amount is deducted from Social Security or paid directly to Medicare.
Figures last verified August 30, 2026.