Working with claims

What’s in an EOB

Each EOB represents one claim and contains:

Who: The patient, provider, and care team.
What: Diagnoses, procedures, and items/services provided.
When: The service period (billable period).
How much: What was billed, what Medicare allowed, and what was paid.
Type: Whether it’s inpatient, outpatient, carrier, pharmacy, etc.

Anatomy of an EOB response

When you request /ExplanationOfBenefit, you get a Bundle of claims:

{
  "resourceType": "Bundle",
  "type": "searchset",
  "total": 89,
  "link": [
    { "relation": "next", "url": "...?startIndex=10&_count=10" }
  ],
  "entry": [
    {
      "resource": {
        "resourceType": "ExplanationOfBenefit",
        "id": "carrier--10045426206",
        "type": { ... },
        "patient": { "reference": "Patient/-20140000000001" },
        "billablePeriod": {
          "start": "2025-01-15",
          "end": "2025-01-15"
        },
        "provider": { "reference": "#provider-org" },
        "contained": [ ... ],
        "careTeam": [ ... ],
        "diagnosis": [ ... ],
        "item": [ ... ],
        "payment": { ... },
        "benefitBalance": [ ... ]
      }
    }
  ]
}

The response is paginated: 10 claims per page by default. See Handling pagination.

Reading line items

Each claim has an item array: one entry per service or product. A doctor visit might have one item; a hospital stay could have dozens.

{
  "item": [
    {
      "sequence": 1,
      "diagnosisSequence": [1],
      "careTeamSequence": [3],
      "category": {
        "coding": [
          {
            "code": "1",
            "display": "Medical care",
            "system": "https://bluebutton.cms.gov/resources/variables/line_cms_type_srvc_cd"
          }
        ]
      },
      "servicedPeriod": {
        "start": "2025-01-15",
        "end": "2025-01-15"
      },
      "adjudication": [ ... ]
    }
  ]
}

Linking items to diagnoses and providers

Items reference other parts of the EOB using sequence numbers:

item.diagnosisSequence: [1] links to diagnosis[].sequence: 1
item.careTeamSequence: [3] links to careTeam[].sequence: 3

{
  "diagnosis": [
    {
      "sequence": 1,
      "diagnosisCodeableConcept": {
        "coding": [
          {
            "code": "Z0000",
            "display": "ENCNTR FOR GENERAL ADULT MEDICAL EXAM W/O ABNORMAL FINDINGS"
          }
        ]
      }
    }
  ],
  "careTeam": [
    {
      "sequence": 3,
      "provider": {
        "identifier": {
          "value": "1234567890"
        }
      },
      "role": {
        "coding": [
          {
            "code": "performing",
            "display": "Performing provider"
          }
        ]
      }
    }
  ]
}

This tells you: item 1 was for diagnosis Z0000 (general medical exam), performed by provider 1234567890.

Understanding adjudication

Every line item has adjudication data showing the financial breakdown of the claim:

{
  "adjudication": [
    {
      "category": {
        "coding": [
          {
            "code": "https://bluebutton.cms.gov/resources/variables/line_sbmtd_chrg_amt",
            "display": "Line Submitted Charge Amount"
          }
        ]
      },
      "amount": {
        "value": 150.00,
        "currency": "USD"
      }
    },
    {
      "category": {
        "coding": [
          {
            "code": "https://bluebutton.cms.gov/resources/variables/line_alowd_chrg_amt",
            "display": "Line Allowed Charge Amount"
          }
        ]
      },
      "amount": {
        "value": 120.00,
        "currency": "USD"
      }
    },
    {
      "category": {
        "coding": [
          {
            "code": "https://bluebutton.cms.gov/resources/variables/line_bene_pmt_amt",
            "display": "Line Payment Amount to Beneficiary"
          }
        ]
      },
      "amount": {
        "value": 96.00,
        "currency": "USD"
      }
    }
  ]
}

Key amounts to look for:

Adjudication code	What it means
`line_sbmtd_chrg_amt`	What the provider billed
`line_alowd_chrg_amt`	What Medicare approved
`line_bene_pmt_amt`	What was paid to the beneficiary
`line_nch_pmt_amt`	What Medicare paid the provider
`line_coinsrnc_amt`	Beneficiary’s coinsurance

Look up all adjudication codes in the Code Systems page.

Claim types

Every EOB has a type field that tells you what kind of claim it is:

Type	Description	Typical content
`CARRIER`	Physician/supplier	Office visits, lab work, outpatient procedures
`INPATIENT`	Hospital inpatient	Hospital stays, surgeries
`OUTPATIENT`	Hospital outpatient	ER visits, same-day procedures
`PDE`	Prescription Drug Event	Pharmacy fills
`DME`	Durable Medical Equipment	Wheelchairs, oxygen, prosthetics
`HHA`	Home Health Agency	Home health visits
`HOSPICE`	Hospice	End-of-life care
`SNF`	Skilled Nursing Facility	Nursing home care

Check the eob-type coding system in EOB.type for these values:

{
  "type": {
    "coding": [
      {
        "code": "CARRIER",
        "system": "https://bluebutton.cms.gov/resources/codesystem/eob-type"
      }
    ]
  }
}

Different claim types populate different fields. Carrier claims emphasize line items and provider info. Inpatient claims have DRG codes and length-of-stay data. PDE claims have drug codes and pharmacy info.

Common fields you’ll actually see

Here are the fields most apps care about:

Field	Path	What it tells you
Claim type	`type.coding[system=eob-type].code`	What kind of claim
Service date	`billablePeriod.start`	When the service happened
Provider	`careTeam[].provider`	Who provided the service
Diagnosis	`diagnosis[].diagnosisCodeableConcept`	ICD-10 diagnosis codes
Amount billed	`item[].adjudication[submitted].amount`	What was charged
Amount paid	`item[].adjudication[benefit].amount`	What Medicare paid
Drug code	`item[].productOrService` (PDE claims)	NDC code for prescriptions
Facility	`facility`	Where the service was provided

For the complete field reference, check the ExplanationOfBenefit endpoint.