California Billing Reference

Medical Billing in California: Payer Landscape, Medicaid & Timely Filing

The working reference for California billing teams: who the payers are, how Medi-Cal managed care is structured, and the filing windows that govern your claims. Updated July 2026.

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Medical Billing in California: The Short Version

California is the most complex billing environment in the country. Medi-Cal — the nation's largest Medicaid program — delivers most care through county-based managed care plans, each with its own portal and authorization rules. Uniquely, California has two separate Blue plans (Anthem Blue Cross and Blue Shield of California), a dominant closed-network HMO in Kaiser Permanente, strict DMHC oversight of managed care, and AB 72 restrictions on out-of-network balance billing.

Payer Landscape

Major Payers in California

Payer	Type	What Billing Teams Should Know
Anthem Blue Cross of California	Commercial / Blue plan	One of TWO California Blues — distinct from Blue Shield of California; separate credentialing and claims
Blue Shield of California	Commercial / Blue plan	Independent nonprofit Blue plan; do not confuse with Anthem Blue Cross
Kaiser Permanente	Integrated HMO	Closed network; out-of-network claims follow Kaiser-specific reimbursement policy
UnitedHealthcare	Commercial / MA	Large employer book; Optum-owned medical groups add referral complexity
Health Net	Commercial / Medi-Cal	Centene-owned; commercial and Medi-Cal lines have different rules
Medi-Cal (DHCS)	Medicaid	6-month filing from end of month of service; county plan assignment controls routing

Medicaid Structure

Medi-Cal: Managed Care Plans

Administered by the California Department of Health Care Services (DHCS). The patient's plan assignment — not just Medicaid eligibility — determines the portal, prior-auth list, and filing rules that apply.

Plan	Notes
L.A. Care Health Plan	Largest publicly operated health plan in the US; Los Angeles County
Health Net (Centene)	Statewide Medi-Cal and commercial presence
Anthem Blue Cross Medi-Cal	Managed Medi-Cal across many counties; separate from commercial Anthem
Molina Healthcare of California	Southern California concentration
Inland Empire Health Plan (IEHP)	Riverside/San Bernardino county-organized plan
CalOptima	Orange County single-plan model
Blue Shield of California Promise	Medi-Cal arm of Blue Shield of California

Filing Deadlines

Timely Filing Limits for California Claims

Initial-claim windows for the payers California practices bill most. Commercial limits are contract-specific — always confirm against your provider agreement and the payer's current manual.

Payer	Timely Filing Limit	Notes
Medi-Cal (fee-for-service)	6 months from end of month of service	Late claims allowed up to 12 months with documented good cause
Medicare (original)	12 months from date of service	Set by federal law; no contract variation
UnitedHealthcare (commercial)	90 days from date of service	Contract-specific; some plans allow 180
Aetna (commercial)	120 days from date of service	Contract-specific; verify provider agreement
Cigna (commercial)	90 days from date of service	Contract-specific; verify provider agreement
Humana (commercial)	90 days from date of service	Among the strictest; Medicare Advantage differs

Verified against payer publications at time of writing (July 2026). Filing limits change by contract and plan year — treat this table as a starting point, not a substitute for the payer manual. See our methodology.

CA-Specific Rules

California Billing Realities to Know

AB 72 Balance Billing

Out-of-network providers rendering care at in-network facilities can generally only collect in-network cost sharing from patients. This reshapes out-of-network strategy for facility-based specialties.

Two Separate Blue Plans

Anthem Blue Cross and Blue Shield of California are unrelated companies. Practices routinely hold two separate Blue contracts with different fee schedules, portals, and filing rules.

DMHC vs CDI Regulation

HMO products answer to the Department of Managed Health Care; some PPOs to the Department of Insurance. Appeal rights and independent medical review pathways differ by regulator.

County-Based Medi-Cal Routing

The same Medi-Cal patient may be billed through different plans depending on county of residence. Eligibility checks must confirm the plan, not just Medi-Cal status.

Frequently Asked Questions

Medi-Cal allows 6 months from the end of the month of service for initial claims, administered by the California Department of Health Care Services (DHCS). Managed care plans operating in California may apply shorter contractual windows, so always verify each plan's provider manual.

L.A. Care Health Plan, Health Net (Centene), Anthem Blue Cross Medi-Cal, Molina Healthcare of California, Inland Empire Health Plan (IEHP), CalOptima, Blue Shield of California Promise. Each plan maintains its own provider portal, prior authorization list, and claim submission rules — the patient's plan assignment, not just Medicaid status, determines how a claim must be billed.

Anthem Blue Cross of California, Blue Shield of California, Kaiser Permanente, UnitedHealthcare, Health Net, alongside Medicare and Medi-Cal. See the payer landscape table on this page for what billing teams should know about each.

AB 72 limits what out-of-network providers can bill patients for non-emergency care delivered at in-network facilities — patients owe only in-network cost sharing, and payment disputes go through an independent process. Facility-based providers (anesthesia, radiology, pathology, assistant surgeons) are most affected.