Construct an X12 837 claim with Coordination of Benefits (COB) loops for secondary-payer submission after a Medicare crossover

Steps

1. Determine whether the claim arrives via automatic Medicare crossover through a Coordination of Benefits Agreement (COBA) trading partner, versus being submitted directly as a secondary claim by the provider, since required loops and balancing rules differ.
2. Populate the SBR segment to correctly sequence primary vs. secondary/tertiary payer responsibility, and repeat Loop 2320 (Other Subscriber Information) once per additional payer beyond the primary.
3. Nest the corresponding Loop 2330 (Other Payer name, identifiers, address) under each 2320 iteration so it applies specifically to that payer, repeating both loops together when more than one additional payer exists.
4. Carry the primary payer's adjudication detail (paid amount, adjustment reasons/amounts) into the claim using CAS and AMT segments within the 2320/2430 loops so the secondary payer can calculate its own liability.
5. For Medicare Secondary Payer (MSP) crossover claims submitted by COBA trading partners, apply CMS's force-balancing convention (an adjustment such as a CAS group/reason code combination in the 2320 or 2430 loop) when the claim would not otherwise balance, per the COBA companion guide.
6. Validate the completed claim against the specific payer's 837 companion guide before submission, since acceptance of COB loops and force-balancing conventions varies by payer/clearinghouse.