Layer 4 resolves payer-specific billing rules that vary significantly between Medicare, Medicaid, and commercial payers. These rules determine filing deadlines, appeal processes, prior authorization requirements, and payment methodology.
Request
If you omit the payer parameter, L4 defaults to Medicare. Pass payer names like Aetna, BCBS, UHC, Cigna, or Medicaid — the resolver maps aliases to the correct profile.
Response (Medicare)
Medicare vs. commercial: side by side
Supported payers
L4 recognizes these payer names and aliases:
Appeal levels
Understanding appeal timelines is critical for denial management:
Medicare appeals (5 levels)
Commercial appeals (2 levels)
Timely filing deadlines are the most common reason for unrecoverable revenue loss. If you miss the filing deadline, the payer can deny the claim with no appeal rights. Always verify the deadline from the L4 response before submitting.
Medicaid state integration
When the payer is Medicaid, L4 enriches the response with the state Medicaid program information from L1:
This cross-layer integration is why L4 depends on L1 — the state determines which Medicaid program and rules apply. 
