Medicare Late Enrollment Penalties in California: How to Avoid Extra Costs

Every year, thousands of Californians pay more than they should for Medicare because they missed an enrollment deadline. Medicare late enrollment penalties are permanent surcharges added to your monthly premiums when you do not sign up during your designated enrollment window. The good news is that these penalties are avoidable if you understand the rules.

This guide explains how penalties work for each part of Medicare, who is most at risk, and what California residents can do to protect themselves.

How Medicare Enrollment Timelines Work

When you first become eligible for Medicare, typically at age 65, you enter a 7-month window called the Initial Enrollment Period (IEP). This window starts 3 months before your 65th birthday month and ends 3 months after it. If you miss the IEP and do not have qualifying coverage through an employer, you may only be able to enroll during the General Enrollment Period (January 1 through March 31 each year), and your coverage will not start until July 1.

That gap between missing your IEP and the start of coverage can leave you uninsured for months. Worse, a late enrollment penalty may follow you for the rest of the time you have Medicare.

The Part B Late Enrollment Penalty

Part B is the most common source of late enrollment penalties. Medicare Part B covers doctor visits, outpatient services, preventive care, and medical equipment. The standard Part B premium in 2026 is $185.00 per month for most people.

If you do not sign up for Part B when you are first eligible and you do not have creditable coverage through a current employer, you will pay an extra 10% for every full 12-month period you could have had Part B but did not. This penalty is added to your monthly premium permanently.

Who is most at risk?

The Part B penalty catches people in a few common situations. Some Californians assume their COBRA coverage counts as employer coverage. It does not. COBRA extends your old plan, but Medicare does not recognize it as a reason to delay Part B enrollment. Others retire at 65 and simply forget to sign up, thinking Medicare starts automatically. Part A may start automatically if you receive Social Security, but Part B requires a separate enrollment step.

Self-employed individuals are another group at risk. If you buy your own health insurance through Covered California or another marketplace, that coverage does not count as employer group coverage for Medicare purposes.

How to avoid the Part B penalty

The most reliable way to avoid the penalty is to enroll in Part B during your IEP. If you are still working at 65 and have coverage through your employer (or your spouse's employer) with 20 or more employees, you can safely delay Part B. When that employment or coverage ends, you will get an 8-month Special Enrollment Period to sign up penalty-free.

If you are approaching 65 and unsure whether your current coverage qualifies, talk to your HR department and ask for a letter confirming your group health plan coverage. You will need this form (CMS-L564) when you eventually enroll in Part B.

The Part D Late Enrollment Penalty

Medicare Part D covers prescription drugs. If you go 63 or more consecutive days without Part D or another form of creditable prescription drug coverage, you may owe a late enrollment penalty when you eventually sign up.

The penalty is calculated as 1% of the national base beneficiary premium multiplied by the number of full months you went without creditable coverage. In 2026, the national base beneficiary premium is approximately $36.78. So each uncovered month adds roughly $0.37 per month to your Part D premium, and this extra cost is permanent.

What counts as creditable drug coverage?

Creditable coverage means the plan covers at least as much as Medicare's standard Part D benefit. Common sources include employer or union drug plans (if they send you a notice saying the coverage is creditable), TRICARE, VA health benefits, and Federal Employee Health Benefits (FEHB). Your plan is required to send you a notice each year telling you whether your drug coverage is creditable.

If you have been keeping those letters, hold onto them. You may need to show proof of creditable coverage to avoid the penalty when you eventually enroll in Part D.

The Part A Late Enrollment Penalty

Most people do not pay a premium for Medicare Part A because they or their spouse paid Medicare taxes for at least 40 quarters (10 years) of work. If you qualify for premium-free Part A, there is no penalty to worry about.

However, if you must buy Part A because you do not have enough work credits, and you do not enroll during your IEP, you face a penalty of 10% of the Part A premium. This penalty lasts for twice the number of years you delayed enrollment. In 2026, the full Part A premium is $518 per month, so a 10% penalty adds $51.80 each month.

This situation is less common but can affect immigrants who arrived in the U.S. later in life and people who worked primarily in jobs not covered by Social Security.

Special Considerations for California Residents

Medi-Cal and penalty relief

If you qualify for both Medicare and Medi-Cal (California's Medicaid program), Medi-Cal may pay your Part B premium, including any late enrollment penalty. Additionally, Medicare Savings Programs in California can help cover premiums, deducibles, and copayments for people with limited income.

Covered California does not prevent penalties

A common misconception in California is that having a Covered California marketplace plan protects you from Medicare penalties. It does not. Marketplace coverage is not considered employer group coverage, and it is not creditable for Medicare purposes. If you are eligible for Medicare, you should transition to Medicare rather than staying on a marketplace plan.

California's large self-employed population

California has one of the highest rates of self-employment in the country. Freelancers, consultants, and small business owners without group health plans need to pay special attention to Medicare enrollment timelines. Individual health insurance, including marketplace plans, does not give you a Special Enrollment Period or protect you from penalties.

What to Do If You Already Have a Penalty

If you are already paying a late enrollment penalty, your options are limited but worth exploring. You can request a reconsideration from Medicare if you believe the penalty was applied in error. For example, if you had employer coverage that should have qualified you for a Special Enrollment Period but your enrollment was processed incorrectly, you can appeal. Contact Medicare at 1-800-MEDICARE (1-800-633-4227) or work with a licensed Medicare agent who can help you file the paperwork.

For Spanish-speaking families navigating Medicare for the first time, our sister site BeneficiosMedicare.com provides step-by-step enrollment guides in Spanish.

Frequently Asked Questions

What is the Medicare Part B late enrollment penalty?

It is a permanent surcharge of 10% added to your monthly Part B premium for every 12-month period you were eligible for Part B but did not enroll. This penalty lasts as long as you have Medicare Part B.

Can I avoid the Part B penalty if I have employer insurance?

Yes. If you or your spouse have health coverage through a current employer with 20 or more employees, you can delay Part B without penalty. When that coverage ends, you get an 8-month Special Enrollment Period to sign up.

How much is the Medicare Part D late enrollment penalty in 2026?

The penalty is 1% of the national base beneficiary premium (about $36.78 in 2026) multiplied by the number of months you went without creditable drug coverage. Each uncovered month adds roughly $0.37 per month to your premium permanently.

Is there a penalty for signing up late for Medicare Part A?

Most people get premium-free Part A and face no penalty. If you must pay for Part A and delay enrollment, the penalty is 10% of the Part A premium, lasting for twice the number of years you were late.