Secondary claim

The secondary claim carries the same services and codes as the primary claim, plus the primary payer’s adjudication. On an electronic 837P the primary’s payment, its contractual adjustment and the amounts it assigned to patient responsibility are reported at claim or line level with the CARC codes the primary used; on paper, the primary’s remittance or EOB goes with the claim. The secondary uses that data to decide whether it pays the balance, part of it, or nothing because the primary already paid at least what the secondary would have allowed.

Secondary balances are small one at a time and large in total. A practice with many dual-coverage patients can have a real share of A/R sitting in secondary status, waiting on a primary remittance to post or on a secondary claim that nobody built. Timely filing applies to the secondary claim too, and payers differ on whether the clock runs from the date of service or from the primary payer’s remittance date, so check the contract. A secondary that pays before the primary becomes a recoupment later.

The mistake is sending the secondary without the primary’s adjustment data, or with amounts that do not reconcile: the billed charge has to equal paid plus adjustments plus patient responsibility, line by line. Clearinghouses reject these up front and payers deny the rest for a missing primary EOB. Post the primary first, let the system build the secondary from the posted remittance, and check that the balance forwarded matches what the primary left open.