QUICK ANSWER: If you already have a Medicare Supplement (Medigap) policy in California, state law gives you an annual window — beginning on your birthday — to switch to another Medigap plan with equal or lesser benefits, with no health questions and no medical underwriting. Carriers in California provide a 60-day window in practice (state law requires at least 30 days). You can switch to a different insurance company, and many people use it to keep the same standardized plan letter at a different premium.

If you've had the same Medigap plan for a few years, you may have noticed your premium creeping up at renewal. Many Californians assume they're locked in — that switching means answering health questions and risking a denial. For most people with an existing Medigap policy, that's not true. California is one of a handful of states with a "Birthday Rule," and it's one of the most useful — and least known — consumer protections in California Medicare insurance.

What the Birthday Rule actually says

California Insurance Code section 10192.11 requires insurers to give existing Medigap policyholders an annual open enrollment period, beginning on the policyholder's birthday, to buy any Medicare Supplement policy that offers benefits equal to or lesser than their current coverage — without medical underwriting. The statute sets a minimum of 30 days; in practice, California carriers provide a 60-day window beginning on your birthday, and insurers are required to notify you of these rights before the window opens. Confirm the exact dates with your carrier or agent, since the notice you receive will state your window.

In plain English: once a year, starting on your birthday, you can shop your Medigap coverage the way you'd shop car insurance — same or lesser coverage level, any carrier that sells it in California, no health questions.

Who can use it

The Birthday Rule is for people who already have a Medigap policy. That includes:

Californians 65 and older with any standardized Medigap plan (G, N, F, and the others). Californians under 65 who have Medicare because of a disability and hold a Medigap policy — California is one of the states that requires carriers to offer Medigap to under-65 beneficiaries (except those with End-Stage Renal Disease), and the Birthday Rule applies to existing policyholders regardless of age.

It is not a way to get your first Medigap policy without underwriting, and it does not apply to Medicare Advantage plans. If you're new to Medicare, your one-time Medigap open enrollment (the 6 months after your Part B effective date) is still the key window — see our turning 65 guide.

What "equal or lesser benefits" means

Medigap plans are standardized by letter, so comparing benefit levels is straightforward:

Same plan letter, different carrier. The most common move. Plan G with Carrier A and Plan G with Carrier B are the same standardized benefits — but the premiums can differ meaningfully. Switching G-to-G at a lower premium is exactly what the rule was designed for.

A lesser plan. You can also step down — for example, from Plan F to Plan G, or from Plan G to Plan N. People sometimes do this deliberately to lower their premium in exchange for picking up a small deductible or copays.

Not a richer plan. You can't use the Birthday Rule to move from Plan N up to Plan G, or from G up to F. Moving to more comprehensive coverage generally requires medical underwriting in California (with limited exceptions, such as certain guaranteed-issue situations).

Birthday Rule vs. Annual Enrollment: don't confuse the two

These trip people up every year, so it's worth being precise:

The Annual Enrollment Period (October 15 – December 7) is for Medicare Advantage and Part D drug plans. It has nothing to do with Medigap. You cannot use AEP to switch Medigap plans without underwriting. Our Annual Enrollment 2026 guide covers what AEP is actually for.

The Birthday Rule is for Medigap only, and it's personal to you — your window runs from your own birthday, whatever time of year that falls.

If you're weighing whether Medigap or Medicare Advantage fits you better in the first place, that's a different decision — our Medicare Advantage vs. Supplement comparison walks through the trade-offs.

What changed (and didn't) in 2026

A California bill, SB 242, would have created an annual open enrollment period allowing all Medicare beneficiaries — including people trying to buy their first Medigap policy — to purchase Medigap coverage without health-based discrimination. That bill did not pass (it died in committee in February 2026). So for 2026, the rules described here are unchanged: the Birthday Rule remains an annual switching right for people who already hold a Medigap policy, not a path into first-time Medigap coverage.

How to use your Birthday Rule window

  1. Watch for your carrier's notice. California requires insurers to notify you of your rights before your window opens.
  2. Note your window. It begins on your birthday. Carriers provide 60 days in practice — your notice will confirm your exact dates.
  3. Compare premiums for your plan letter (or a lesser one). Rates for the same standardized plan vary by carrier, and how a carrier prices by age matters too.
  4. Apply during the window and state that you're using the Birthday Rule. The application should be processed without health questions for qualifying switches.
  5. Don't cancel your old policy until the new one is confirmed in force. Avoid any gap in coverage.

An independent agent can run the comparison across carriers at no cost to you — in Southern California, that's exactly the kind of once-a-year checkup I help clients with, from Los Angeles to San Diego to Santa Barbara. What you pay for Medigap is only one piece of your total Medicare cost picture — our Medicare costs guide covers the rest.

California Birthday Rule FAQs

Does the Birthday Rule apply to Medicare Advantage plans?
No. It applies only to Medicare Supplement (Medigap) policies. Medicare Advantage changes happen during the Annual Enrollment Period (Oct 15 – Dec 7) or the Medicare Advantage Open Enrollment Period (Jan 1 – Mar 31), or a Special Enrollment Period if you qualify.
Can I switch insurance companies, or only plans?
You can do either. The rule lets you buy an equal-or-lesser plan from any carrier selling Medigap in California — same letter with a different company is the most common switch.
Can I upgrade from Plan N to Plan G during my birthday window?
No. The Birthday Rule only covers switches to plans with equal or lesser benefits. Moving to richer coverage generally requires medical underwriting.
I have Medicare under 65 because of a disability. Does the rule apply to me?
If you already hold a California Medigap policy, yes — the annual switching right applies to existing policyholders. California also requires carriers to offer Medigap to under-65 beneficiaries (except ESRD) during their initial open enrollment.
Do other states have a Birthday Rule?
A handful do — including Oregon, Nevada, Idaho, and others — but the details (window length, what you can switch to) differ by state. This article covers California only.
Does using the Birthday Rule cost anything?
No. There's no fee to switch, and help from an independent agent is free to you — agents are paid by the insurance carriers, and the premium is the same either way.

Sources & official references

Last reviewed: July 2026. Medicare and Medigap rules can change — confirm current rules at Medicare.gov and with the California Department of Insurance. Educational information only, not individualized advice.