This page goes further than the basics: how Part D really works, what happens if you enroll late, how income affects what you pay, and — just as important — what Medicare doesn't cover. Use the jump links below to go straight to what you need.
Part D is more layered than people expect. Here's how a typical plan year actually unfolds.
You pay out of pocket first, up to your plan's deductible (no more than $615 in 2026 — many plans charge less).
After the deductible, you and your plan share costs — you typically pay a copay or coinsurance for each prescription.
Once your out-of-pocket spending hits the annual cap, you pay $0 for covered drugs for the rest of the year — a major recent improvement.
Coverage that's expected to pay, on average, at least as much as standard Medicare drug coverage — most employer plans qualify, but not all. If you have employer coverage when you turn 65, ask your HR department directly whether it's creditable; they're required to tell you in writing each year.
If your income and resources are limited, the Extra Help program can lower or eliminate your Part D premium, deductible, and copays — and if you qualify, you're also protected from the late enrollment penalty.
Missing your enrollment window without a qualifying exception doesn't just mean a one-time fee — for Part B and Part D, it means a permanent addition to your premium for as long as you have that coverage.
Adds 10% to the standard Part B premium for every full 12-month period you went without Part B (or other creditable coverage, like an active large-employer plan) after becoming eligible.
Example: wait 2 full years → pay 20% more, permanently. In 2026, that's roughly $243.50/month instead of $202.90.
Adds 1% of the national base beneficiary premium ($38.99 in 2026) for every full month you went without creditable drug coverage, once 63+ days have passed.
Example: go 14 months without coverage → pay roughly $5.50/month extra, permanently, on top of your plan's premium.
Get a rough estimate of what a Part B or Part D late enrollment penalty could look like, based on 2026 figures.
Only count full 12-month periods after your Initial Enrollment Period ended.
Only counts once you've gone 63+ continuous days without creditable coverage.
This calculator gives a rough estimate using standard 2026 figures published by Medicare.gov and CMS. It doesn't account for special enrollment periods, Extra Help eligibility, or other exceptions that could mean you owe no penalty at all. Your actual penalty is determined by the Social Security Administration — if you've received a penalty notice and think it's wrong, you can appeal it. Reach out if you'd like help figuring out your specific situation.
If your income is above certain thresholds, you'll pay more than the standard premium for both Part B and Part D — regardless of which plan you choose. IRMAA is based on your tax return from two years earlier (2026 premiums use your 2024 income), and it's a cliff, not a gradual scale: $1 over a threshold triggers the entire next tier.
| Individual MAGI | Joint MAGI | Monthly IRMAA | Total Part B Premium |
|---|---|---|---|
| $109,000 or less | $218,000 or less | $0.00 | $202.90 |
| $109,001 – $137,000 | $218,001 – $274,000 | $81.20 | $284.10 |
| $137,001 – $171,000 | $274,001 – $342,000 | $202.90 | $405.80 |
| $171,001 – $205,000 | $342,001 – $410,000 | $324.60 | $527.50 |
| $205,001 – $499,999 | $410,001 – $749,999 | $446.30 | $649.20 |
| $500,000 or more | $750,000 or more | $487.00 | $689.90 |
Source: CMS, "2026 Medicare Parts A & B Premiums and Deductibles" (released Nov 14, 2025).
Part D IRMAA uses the same income brackets as Part B, but the surcharge is a separate, smaller dollar amount added on top of whatever your Part D plan's own premium is.
| Individual MAGI | Joint MAGI | Monthly Part D IRMAA |
|---|---|---|
| $109,000 or less | $218,000 or less | $0.00 |
| $109,001 – $137,000 | $218,001 – $274,000 | $14.50 |
| $137,001 – $171,000 | $274,001 – $342,000 | $37.50 |
| $171,001 – $205,000 | $342,001 – $410,000 | $60.40 |
| $205,001 – $499,999 | $410,001 – $749,999 | $83.30 |
| $500,000 or more | $750,000 or more | $91.00 |
Part D IRMAA is paid directly to Medicare (via Social Security deduction or a separate bill) — not to your Part D plan — even if a third party pays your plan premium for you.
Original Medicare covers a lot, but it has real, well-known gaps. Knowing them in advance is the whole point of supplemental coverage.