3.5 Late Enrollment Penalties (Part A, Part B, Part D)
Key Takeaways
- The Part B late-enrollment penalty is 10% of the standard premium for each full 12-month period a beneficiary was eligible but not enrolled without creditable coverage, and it lasts as long as they have Part B.
- The Part D late-enrollment penalty is 1% of the national base beneficiary premium ($38.99 in 2026) times the number of full months without Part D or other creditable drug coverage, added permanently to the Part D premium.
- The rare Part A late-enrollment penalty (for beneficiaries who must buy Part A) is a 10% premium increase paid for twice the number of years the person delayed enrollment — not permanently.
- Having other creditable coverage — such as active employer group coverage — at the time of IEP prevents all of these penalties from starting, as long as the beneficiary enrolls promptly after that coverage ends.
- Income-Related Monthly Adjustment Amount (IRMAA) is a separate, income-based premium surcharge and is NOT a late-enrollment penalty — the exam tests this distinction directly.
Why Penalties Matter on the Exam
Every enrollment-timing rule in this chapter exists partly to explain why a beneficiary would owe a late-enrollment penalty. AHIP consistently tests whether you can (1) identify that a penalty applies, (2) calculate its approximate size, and (3) recognize when an exception — usually a form of creditable coverage — prevents it. Because these penalties are frequently permanent, correctly advising a client here has real, lasting financial consequences, which is exactly why the exam treats this material as high-stakes.
The Three Penalties at a Glance
| Part | Trigger | Penalty Formula | How Long It Lasts |
|---|---|---|---|
| Part A (rare — only those who must buy it) | Delaying purchase of premium Part A past IEP without creditable coverage | 10% premium increase | Twice the number of years delayed (not permanent) |
| Part B | Eligible but not enrolled, and no creditable coverage (e.g., current employer group coverage) | 10% of the standard Part B premium per each full 12-month period delayed | Permanent, for as long as the person has Part B |
| Part D | 63+ consecutive days without Part D or other creditable drug coverage after the IEP ends | 1% of the national base beneficiary premium ($38.99 in 2026) × number of full months without coverage, rounded to the nearest $0.10 | Permanent, for as long as the person has Part D |
Part B Penalty — Worked Example
The Part B penalty is calculated in whole 12-month blocks of delay, not prorated months.
Worked example: Mr. Ferris became eligible for Part B at 65 but did not enroll and had no employer coverage. He waited 30 months (2 full 12-month periods, with a partial third period that does not count) before enrolling during a later General Enrollment Period. His penalty is 20% of the standard Part B premium (10% × 2 full years), added to his premium for as long as he has Part B — not for a fixed number of years like the Part A penalty.
Using the 2026 standard Part B premium of $202.90/month, a 20% penalty adds roughly $40.58/month on top of the standard premium, indefinitely.
Part D Penalty — Worked Example
The Part D penalty is based on full months, calculated against the national base beneficiary premium, which is $38.99 for 2026.
Worked example: Ms. Alvarado's IEP ended in June, and she did not enroll in Part D or have other creditable drug coverage until she signed up during AEP for a January 1 start — a gap of 7 full months. Her monthly penalty is 1% × $38.99 × 7 = $2.73/month (rounded to the nearest $0.10), added to whatever her chosen plan's premium is, for as long as she keeps Part D coverage. Note that this base figure is recalculated each year, so the dollar penalty can shift slightly year to year even though the "months late" figure never changes.
What Prevents the Penalty: Creditable Coverage
The single biggest penalty-avoidance concept on the exam is creditable coverage — coverage (most often from a current employer or union) that CMS considers at least as good as standard Medicare coverage. As long as a beneficiary has creditable coverage through their IEP and enrolls in Medicare or Part D within the appropriate SEP window after that coverage ends (typically the 63-day SEP covered in Section 3.4), no penalty accrues for the period they were covered elsewhere.
Worked example: Mr. Kwan works past 65 and stays on his employer's group health plan, which includes creditable drug coverage. He retires at 68 and enrolls in Part D within 63 days of losing that coverage. Even though 3 years passed between his IEP and his Part D enrollment, he owes no Part D penalty, because the entire gap was covered by creditable coverage.
The IRMAA Trap
The exam frequently pairs late-enrollment penalty questions with a distractor about IRMAA (Income-Related Monthly Adjustment Amount). These are not the same thing:
| Late-Enrollment Penalty | IRMAA | |
|---|---|---|
| Trigger | Enrolling late without creditable coverage | Having income above a CMS-set threshold |
| Applies to | Parts A (rare), B, and D | Parts B and D |
| Purpose | Penalizes delayed enrollment | Higher-income beneficiaries pay a larger share of program cost |
| Based on | Months/years of delay | Modified Adjusted Gross Income (MAGI) from IRS tax data |
A high-income beneficiary who enrolled exactly on time can still pay more than the standard premium because of IRMAA — that additional amount is not a "penalty" in the late-enrollment sense, and describing it as one is a common error the exam will flag as incorrect.
Common Exam Traps
- Treating the Part B penalty as a fixed dollar amount rather than a percentage of the current standard premium (it recalculates whenever the premium changes).
- Forgetting that the Part A penalty (unlike B and D) is not permanent — it ends after twice the delay period.
- Missing that the Part D penalty is based on the national base beneficiary premium, not the beneficiary's own plan's premium.
- Confusing IRMAA with a late-enrollment penalty — they have entirely different triggers and purposes.
A beneficiary was eligible for Part B for 25 months without creditable coverage before finally enrolling. How many full 12-month periods count toward the Part B late-enrollment penalty, and what is the resulting penalty percentage?
Which of the following correctly describes the difference between a late-enrollment penalty and IRMAA?
Mr. Osei kept creditable prescription drug coverage through his employer until age 70, then enrolled in a stand-alone Part D plan within 60 days of losing that coverage. What Part D late-enrollment penalty does he owe?