How does secondary billing work with medicare as primary?

How does secondary billing work with medicare as primary?

How Does Secondary Billing Work with Medicare as Primary?

When Medicare is the primary insurance, billing a secondary payer—such as a commercial plan, Medicaid, or a supplemental policy—follows a structured process. Understanding how secondary billing works in this scenario helps ensure proper payment and reduces claim denials or billing delays.

1. Medicare as the Primary Payer

Medicare is considered primary when:

  • The patient is retired and not covered by an employer group plan

  • The patient has Medicare due to age or disability and does not have another plan with primary status

  • No other insurance takes precedence under Medicare Secondary Payer (MSP) rules

Once Medicare processes a claim, the Medicare Explanation of Benefits (EOB) (also called the Medicare Remittance Advice) becomes the foundation for secondary billing.

2. Identify the Type of Secondary Coverage

Common types of secondary payers to Medicare include:

  • Medigap (Medicare Supplement Insurance): Covers some or all of the remaining deductible, coinsurance, and copayments

  • Medicaid: May act as a secondary payer for patients who qualify for both Medicare and Medicaid (“dual eligibles”)

  • Commercial Insurance or Employer Group Plans: Can be secondary under specific COB rules

Tip: Knowing the type of secondary insurance determines how and what to bill.

3. Use Medicare Crossover Billing When Available

Medicare crossover allows Medicare to automatically forward processed claims to the secondary payer, eliminating the need to submit a second claim manually.

  • If the patient’s secondary plan is registered with Medicare’s Coordination of Benefits Contractor (COBC), claims will crossover automatically

  • You’ll receive a message on the remittance advice stating the claim was forwarded

  • No action is needed unless the secondary payer requires additional documentation

Important: Always verify if the patient’s secondary is enrolled for crossover.

4. Manual Secondary Billing (When Crossover Is Not Available)

If the claim doesn’t crossover automatically, you’ll need to:

  • Submit the claim manually to the secondary insurance

  • Include a copy of the Medicare EOB

  • Ensure that patient demographics and insurance details match what’s on file with the secondary payer

Best practice: Double-check payer-specific requirements for submitting secondary claims after Medicare.

5. Special Considerations for Medicaid as Secondary

If Medicaid is the secondary payer:

  • It will only pay after all other payers have paid or denied

  • Medicaid may require prior authorization for certain services—even if Medicare doesn’t

  • The provider must be enrolled and credentialed with the state Medicaid program

  • Medicaid typically pays the lesser of the remaining balance or its fee schedule rate

Note: Medicaid is always considered the payer of last resort.

6. Monitor Timely Filing Limits

Each secondary payer has its own timely filing policy, often ranging from 60 to 180 days from the date Medicare processes the claim. Failure to submit within this window can result in denials.

7. Don't Bill the Patient Prematurely

Wait until the secondary payer processes the claim before billing the patient. This ensures:

  • Accurate out-of-pocket calculation

  • No risk of overcollection

  • Compliance with billing regulations for Medicare beneficiaries

Conclusion:

When Medicare is the primary payer, secondary billing depends on the type of secondary insurance and whether crossover billing is active. By understanding the coordination rules, submitting claims correctly, and tracking payer responses, your practice can improve reimbursement while minimizing billing errors.

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