Who Pays First: Medicare or Medicaid?

Your parent just had a doctor's visit. They have both Medicare and Medicaid. The billing department is confused, the claim was denied, and now someone is asking your parent to pay out of pocket. Before anyone writes a check, there's one rule you need to know: when Medicare and Medicaid are the relevant coverage, Medicare generally pays first, but employer, retiree, no-fault/liability, or workers' compensation coverage can take priority.

The Payment Hierarchy

For dual eligible beneficiaries—people enrolled in both Medicare and Medicaid—the payment order depends on whether another payer has priority. When Medicare and Medicaid are the relevant coverage, federal coordination rules generally place Medicare first:

1. Medicare pays first (primary payer) for all Medicare-covered services
2. Medicaid pays second (secondary payer) for remaining costs and services Medicare doesn't cover

Medicaid is always the payer of last resort. It steps in after Medicare and any other insurance have processed their shares.

This hierarchy extends to more complex insurance situations:

The key takeaway: Medicaid is the payer of last resort and does not pay first when another coverage has priority.

How Claims Cross Over

In practice, when no other payer has priority, the billing process for dual eligible patients is largely automated. Here's what happens when your parent visits a doctor:

1. The provider submits the claim to Medicare
2. Medicare processes the claim and pays its portion (typically 80% of the approved amount for Part B services)
3. The remaining cost sharing (deductibles, coinsurance, copays) generally crosses over electronically to Medicaid
4. Medicaid processes the crossover claim and pays up to its state-set rate

For Qualified Medicare Beneficiary (QMB) enrollees, this crossover eliminates all patient responsibility. Medicare pays first, Medicaid covers the cost sharing, and the patient owes nothing. Providers are federally prohibited from billing QMB patients for any Medicare cost sharing—even if Medicaid pays nothing toward that cost sharing due to state rate caps.

What Medicaid Covers That Medicare Doesn't

The "payer of last resort" role means Medicaid picks up categories of care that Medicare simply doesn't touch:

• Long-term custodial nursing home care (Medicare covers only short-term skilled rehabilitation, capped at 100 days)
• Personal care assistance (bathing, dressing, eating, toileting)
• Home and Community-Based Services (HCBS waiver programs)
• Non-emergency medical transportation (rides to doctor appointments)
• Dental, vision, and hearing (limited or absent under Medicare; covered by many state Medicaid programs)
• Medicare premiums (for QMB, SLMB, and QI enrollees)

For dual eligible seniors, this combination provides the most comprehensive public coverage available—acute medical care through Medicare plus long-term supportive care through Medicaid.

Common Billing Problems and How to Fix Them

The Provider Bills Your Parent Directly

If your parent is QMB-enrolled, they should never receive a bill for Medicare cost sharing under the federal QMB prohibition. If a bill arrives:

1. Call the billing office and state that the patient is dual eligible/QMB-enrolled
2. Provide the Medicaid ID number so the provider can submit the crossover claim
3. If they refuse, cite CMS publication MLN7936176 (the federal prohibition on balance billing QMB patients)
4. Report persistent violations to 1-800-MEDICARE

A Claim Is Denied Because the Provider Filed with the Wrong Payer

Providers unfamiliar with dual eligibility sometimes bill Medicaid first. For a Medicare-covered service, ask the provider to resubmit the claim to Medicare. Once Medicare processes its share, the claim generally crosses over electronically to Medicaid.

The Provider "Doesn't Accept Medicaid"

This doesn't matter for QMB cost-sharing protection. Any Medicare-participating provider is prohibited from billing QMB patients for Medicare cost sharing, regardless of whether they participate in Medicaid. The protection follows the patient, not the provider's Medicaid status.

D-SNPs Simplify Coordination

For dual eligible seniors enrolled in a Dual Eligible Special Needs Plan (D-SNP), the plan coordinates Medicare and Medicaid benefits, but the degree of integration varies by model. Highly integrated plans can reduce billing errors and the need for families to manually track which program pays for what.

Fully Integrated D-SNPs (FIDE-SNPs) take this further by holding both Medicare and Medicaid contracts under one entity, creating a single point of contact for all coverage questions, claims issues, and appeals.

The Dual Eligible Coordination Blueprint maps the complete payment hierarchy and includes dispute letter templates for resolving billing errors when providers mishandle dual eligible claims.

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