What is a secondary claim?
A secondary claim bills a patient's second insurer for what the primary didn't pay, with the primary's payment details attached. Medicare often sends it automatically as a crossover.
Secondary claim, from the primary's remittance
- Primary
- Medicare, paid 03/20/2026
- Secondary
- Example Medigap Plan G
| Service | Billed | Primary allowed | Primary paid | Sent to secondary |
|---|---|---|---|---|
| 99214 Office visit | $210.00 | $128.40 | $102.72 | $25.68 coinsurance |
- If the Medicare remittance carries remark MA18, the claim was crossed over automatically. Sending it again creates a duplicate.
When a patient has two plans, the coordination of benefits order decides who pays first. Once the primary pays, the remaining balance goes to the secondary, along with how the primary processed each line.
Crossover or manual?
Medicare automatically forwards many claims to supplemental insurers and Medicaid through its crossover program, and says so on the remittance with remark MA18. Other primaries don’t, so the provider has to send the secondary claim itself, electronically with the primary’s adjudication or on paper with the primary’s EOB.
Why secondaries are left on the table
Secondary balances are small per claim and easy to forget. A crossover that never arrived, a secondary claim sent before the primary paid, or a missing EOB attachment each leave money sitting in A/R until it’s past the secondary’s filing limit.
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