> ## Documentation Index
> Fetch the complete documentation index at: https://docs.rcintell.com/llms.txt
> Use this file to discover all available pages before exploring further.

# L4: Payer

> Resolve payer-specific rules including timely filing, appeal levels, prior authorization, and secondary payer rules

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

```bash theme={null}
curl "https://api-dev.rcintell.com/v1/knowledge/layers/170001/l4?payer=Medicare" \
  -H "X-API-Key: $RCI_API_KEY"
```

<Note>
  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.
</Note>

## Response (Medicare)

```json theme={null}
{
  "layer": "l4_payer",
  "data": {
    "payer_name": "Medicare",
    "payer_type": "federal",
    "timely_filing_federal": "12 months from date of service",
    "appeals_levels": [
      "Redetermination (60 days)",
      "Reconsideration - QIC (180 days)",
      "ALJ Hearing ($180 threshold)",
      "Medicare Appeals Council",
      "Federal District Court ($1,760 threshold)"
    ],
    "secondary_payer_rules": "Medicare Secondary Payer (MSP) rules apply",
    "advance_beneficiary_notice": true,
    "assignment_rules": "Participating providers must accept assignment"
  }
}
```

## Medicare vs. commercial: side by side

| Rule                | Medicare                                   | Aetna (commercial)                               |
| ------------------- | ------------------------------------------ | ------------------------------------------------ |
| **Timely filing**   | 12 months from DOS                         | Varies by contract (typically 90-365 days)       |
| **Appeal levels**   | 5 levels (Redetermination → Federal Court) | 2 levels (Internal appeal → External review)     |
| **Prior auth**      | Limited (mostly DME, some surgical)        | Required for many services — check specific plan |
| **Payment basis**   | MPFS (RVU-based)                           | Contracted fee schedule or % of Medicare         |
| **Balance billing** | Limited by assignment                      | Depends on network status                        |
| **Secondary payer** | MSP coordination rules                     | Coordination of benefits (COB)                   |

## Supported payers

L4 recognizes these payer names and aliases:

| Input value                                             | Resolves to                      | Type    |
| ------------------------------------------------------- | -------------------------------- | ------- |
| `Medicare`, `CMS`                                       | Medicare                         | Federal |
| `Medicaid`, `KanCare`, `Medi-Cal`                       | Medicaid (state-specific via L1) | State   |
| `Aetna`, `Cigna`, `BCBS`, `Blue Cross`, `UHC`, `United` | Commercial                       | Private |
| `TRICARE`                                               | TRICARE                          | Federal |
| `Self-Pay`, `Cash`                                      | Self-Pay                         | None    |

## Appeal levels

Understanding appeal timelines is critical for denial management:

### Medicare appeals (5 levels)

| Level | Name                     | Deadline                       | Threshold                     |
| ----- | ------------------------ | ------------------------------ | ----------------------------- |
| 1     | Redetermination          | 120 days from remittance       | —                             |
| 2     | Reconsideration (QIC)    | 180 days from Level 1 decision | —                             |
| 3     | ALJ Hearing              | 60 days from Level 2 decision  | \$180 amount in controversy   |
| 4     | Medicare Appeals Council | 60 days from Level 3 decision  | —                             |
| 5     | Federal District Court   | 60 days from Level 4 decision  | \$1,760 amount in controversy |

### Commercial appeals (2 levels)

| Level | Name            | Typical deadline                           |
| ----- | --------------- | ------------------------------------------ |
| 1     | Internal appeal | 30-180 days (varies by state and contract) |
| 2     | External review | State-mandated independent review          |

<Warning>
  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.
</Warning>

## Medicaid state integration

When the payer is Medicaid, L4 enriches the response with the state Medicaid program information from L1:

```bash theme={null}
curl "https://api-dev.rcintell.com/v1/knowledge/layers/170001/l4?payer=Medicaid" \
  -H "X-API-Key: $RCI_API_KEY"
```

```json theme={null}
{
  "layer": "l4_payer",
  "data": {
    "payer_name": "Medicaid",
    "payer_type": "state",
    "notes": "Rules vary by state — see L1 Medicaid program details",
    "crossover_claims": "Automatic crossover for Medicare/Medicaid dual-eligible",
    "state_program": {
      "program_name": "KanCare",
      "url": "https://portal.kmap-state-ks.us"
    }
  }
}
```

This cross-layer integration is why L4 depends on L1 — the state determines which Medicaid program and rules apply.