Plain version: California adds its own layer on top of the federal Medigap rules: which plans an insurer must offer, how Medicare Select works, and when an insurer must accept an applicant regardless of health.
Required plans: according to the CDI outline, insurers offering Medicare supplement policies must offer Plan A and either Plan C or Plan F. Current law adds detail: every issuer must make Plan A available; an issuer that offers any additional benefit must also make available Plan C or Plan F, and for people newly eligible for Medicare on or after January 1, 2020, that requirement reads as Plan D or Plan G.
Medicare Select (§10192.10): a Medicare supplement policy with restricted network provisions, meaning payment of benefits depends in whole or in part on using network providers. It still may not restrict payment for emergency care, or for services immediately required for an unforeseen illness, injury or condition when using a network provider is not reasonable.
Preexisting conditions: a Medicare supplement policy may not exclude or limit benefits for losses incurred more than six months after the effective date because of a preexisting condition. So even when an insurer may underwrite, the exclusion can last at most six months.
Open enrollment (§10192.11):
Six-month period beginning the first day of the first month a person is both 65 or older and enrolled in Part B. The clock starts with Part B, not the 65th birthday. During it, the issuer may not deny the application because of health.
California's birthday rule: a person covered by a Medicare supplement policy has an annual open enrollment of 60 days or more, starting on the birthday. It protects only a move to a policy with benefits equal to or lesser than the current coverage.
Application questions (§10192.18): the required application asks, for example, whether the applicant turned 65 or enrolled in Part B in the last six months, and about other Medicare plans or Medigap policies. It also asks about Medi-Cal; the form's note tells a person who has a Medi-Cal share of cost to answer NO to that question.