The California Birthday Rule for Medigap: How It Works in 2026

If you've had the same Medicare Supplement plan — most people call it Medigap — 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.

Prefer to watch? Matt explains the Birthday Rule in about 3 minutes.

What the Birthday Rule actually says

California Insurance Code section 10192.11(h) entitles an existing Medicare Supplement policyholder to "an annual open enrollment period lasting 60 days or more, commencing with the individual's birthday," during which that person may buy any Medicare Supplement policy offering benefits equal to or lesser than their current coverage — without medical underwriting or health-based pricing. The 60-day length has been California law since January 1, 2020, when SB 407 replaced the earlier 30-day window. Insurers must also notify you of these rights 30 to 60 days before your window opens, and again on any notice about a benefit change or premium adjustment.

A common point of confusion. A number of websites describe California's window as "60 days from the first day of your birth month." The statute reads differently: the window commences with your birthday, and 60 days is a minimum, not a maximum. Because carriers are free to be more generous than the law requires, practice can vary — check your carrier's bulletin, since windows can start on your birthday or, with some carriers, the first of your birth month. Whatever the notice you receive says is what governs your application.

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.

When is my Birthday Rule window?

Your window opens on your birthday — the actual date, not the first of the month — and runs at least 60 days. Here is roughly where the 60-day minimum lands for each birth month, depending on whether your birthday falls early or late in the month:

These closing dates are approximations built from the 60-day statutory minimum — count 60 days forward from your own birthday for a closer estimate. Your exact opening and closing dates come from your carrier, and the notice it sends 30 to 60 days ahead of the window will state them. Some carriers allow longer than 60 days, so never assume a window has closed without checking.

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. Not sure the Birthday Rule is the window you need? See all the ways to change a Medigap plan in California without underwriting.

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. The Plan F to Plan G step-down is the most common one — here is how the Part B deductible math works.

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. It's also just one of four windows for changing a Medigap plan — our guide to when you can change your Medigap plan in California covers the full list, including guaranteed-issue rights.

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 was returned to the Secretary of the Senate on February 2, 2026 under Joint Rule 56, which ended its run. 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 and runs at least 60 days by law — 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 the carriers they represent at no cost to you, because agents are paid by the insurance carriers — 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. If you would rather start with someone close to home before your window opens, our guide to finding a Medicare broker near you lists the areas I cover. 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.

Is the Birthday Rule the same for Medigap and Medicare Supplement plans?

Yes — those are two names for the same thing. "Medicare Supplement" is the formal name used in California Insurance Code and on your policy documents; "Medigap" is the nickname used by Medicare.gov and most agents. There is one Birthday Rule, and it applies to standardized Medicare Supplement (Medigap) plans in California no matter which name your carrier prints on the paperwork.

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 regardless of age. California also requires carriers to make Medicare Supplement coverage available to under-65 beneficiaries who do not have End-Stage Renal Disease, during a six-month open enrollment that starts with Part B; the statute limits that offer to certain plan letters, so ask your carrier or agent which ones are available to you.

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

• California Insurance Code § 10192.11 — annual open enrollment (birthday rule)
• California Department of Insurance — Medicare Supplement insurance guide
• California Department of Aging — HICAP Medicare counseling (California’s SHIP)
• Medicare.gov — Medigap basics
• California SB 407 (2019) — extended the birthday-rule window to 60 days
• California Legislature — SB 242 (2025–26 session) bill status

Last reviewed: September 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.