HL7 Table HL70203: Identifier Type Code

HL70203 is the flagship identifier-semantics table in HL7 v2. It declares what kind of identifier a CX composite is carrying — a medical record number, a Social Security number, a driver's license, an NPI, an account number, a visit number, and many more — by populating CX.5 Identifier Type Code with one of the table's short alphabetic codes. The table is HL7-defined but allows local extension (it is sometimes described as "user-defined with HL7 suggested values"), making it the most operationally extended code table in the v2 catalogue.

Purpose

Identifiers in v2 are positional and ambiguous unless tagged. The string 123-45-6789 is meaningless without a label saying it is a Social Security number. HL70203 supplies that label. A receiver reading 123-45-6789^^^USA^SS immediately knows the value is an SSN and can route it to the SSN-handling logic without inferring the type from CX.4 (assigning authority) or out-of-band agreements.

The table is also the linchpin of v2-to-FHIR identifier mapping: FHIR Identifier.type.coding is bound directly to the HL70203 ValueSet, so a faithful FHIR translation of any CX composite hinges on getting CX.5 right.

Where it's used

• CX.5 Identifier Type Code — every CX composite in the spec, which means PID-2, PID-3, PID-4, NK1-33, GT1-2, IN1-49, ORC-12, and many more.
• PID-3 Patient Identifier List, with one CX per identifier — MR for the MRN, SS for the SSN, DL for the driver's license, etc.
• PV1-19 Visit Number (with type code VN).
• Most extended-composite identifier fields across ADT, ORM, ORU, BAR, and SIU messages.

Code list

The list below is the v2.8.1 set, filtered to the codes most commonly seen on production interfaces. The full HL70203 includes additional administrative and financial codes; consult the HL7 Terminology CodeSystem for the exhaustive list.

Code system OID

• OID: 2.16.840.1.113883.18.108
• Canonical URI: http://terminology.hl7.org/CodeSystem/v2-0203

This OID is emitted in CX.9 when a profile demands OID-bound coded type values.

HL7-defined vs user-defined

HL70203 is HL7-defined with extensibility. The HL7 codes above are normative, but the table explicitly allows local extension for identifier types that do not appear in the suggested set. Local extensions must not collide with HL7 codes and should be registered in the site's interface specification.

In practice, the table is one of the most-extended in HL7: payers, government agencies, and large health systems routinely add codes for their own identifier classes.

Version differences

• v2.2 — Initial small set: MR, SS, EI, PI, VN, DL.
• v2.3 — Major expansion: NPI predecessor codes, payment-card codes (AM, MS, VS, DS, DI), guarantor codes.
• v2.5 — NPI added formally after the CMS Final Rule. UPIN reclassified as legacy.
• v2.6 — APRN, RPH, RN added for non-physician licensure. NNxxx pattern added for ISO-coded national identifiers.
• v2.7 — Several anonymized/temporary codes added (APN, MRT, PNT, TPR).
• v2.8 – v2.8.1 — Set largely stable; minor display-string edits.

Common mistakes

• Using MR and PI interchangeably. MR is the canonical medical record number issued by a hospital; PI is an internal patient identifier that may be distinct (e.g., an enterprise master-patient-index ID). Collapsing them loses semantic precision and breaks FHIR Patient.identifier slicing.
• Sending SSN instead of SS. HL70203 codes are short alphabetic literals; multi-character variants like SSN, MRN, or DLN are not valid.
• Using NPI in CX.5 without populating CX.4 with the US NPI assigning authority OID (2.16.840.1.113883.4.6). The type code alone is not enough for unambiguous downstream consumption.
• Treating VN as a patient identifier. VN is the visit number and belongs in PV1-19, not PID-3.
• Inventing local codes that collide with HL7 codes (e.g., redefining DL to mean "Department List"). Local extensions must use new codes, not redefine the standard ones.

Examples

A PID-3 list with MRN, SSN, and driver's license:

PID|1||10456^7^M10^HOSPITAL^MR~123-45-6789^^^USA^SS~D1234567^^^MA-DMV^DL||DOE^JANE

NPI on a provider XCN inside ORC-12:

ORC|RE|||||||||||1234567893^SMITH^JOHN^^^^^^&2.16.840.1.113883.4.6&ISO^L^^^NPI

Visit number on PV1-19:

PV1|1|I|2W^201^A^HOSPITAL||||||||||||||||V20260626001^^^HOSPITAL^VN

A FHIR Patient.identifier translation preserving HL70203 in type.coding:

{
  "identifier": [{
    "type": {
      "coding": [{
        "system": "http://terminology.hl7.org/CodeSystem/v2-0203",
        "code": "MR",
        "display": "Medical record number"
      }]
    },
    "system": "urn:oid:2.16.840.1.113883.19.5.99999.1",
    "value": "10456"
  }, {
    "type": {
      "coding": [{
        "system": "http://terminology.hl7.org/CodeSystem/v2-0203",
        "code": "SS"
      }]
    },
    "system": "http://hl7.org/fhir/sid/us-ssn",
    "value": "123-45-6789"
  }]
}

FHIR mapping

The v2-to-FHIR IG does not publish a ConceptMap for this table; the mapping below follows the obvious correspondence, preserving the HL70203 codes verbatim and binding them to Identifier.type.coding under the canonical CodeSystem http://terminology.hl7.org/CodeSystem/v2-0203. The mapping is one-to-one for the standard codes; local extensions ride through unchanged but must use a stable system URI.

FHIR additionally provides a smaller, opinionated value set at http://terminology.hl7.org/ValueSet/identifier-type (DL, PPN, BRN, MR, MCN, EN, TAX, NIIP, PRN, MD, DR, SB, ANON, TEMP, WP, RI, etc.) that overlaps HL70203 but is intentionally narrower. Most v2-to-FHIR pipelines bind to the full v2-0203 set rather than the abbreviated FHIR set to avoid losing information.

Engine considerations

• Slicing on FHIR output — Identifier.type.coding.code is the natural slice discriminator for FHIR Patient, Practitioner, and Organization. Engines should preserve CX.5 faithfully to keep the slices stable.
• Round-trip safety — When a local code is encountered, do not silently coerce to U or USID; preserve the original code with a custom system URI so the outbound v2 channel can restore it.
• Type vs assigning authority — CX.5 is the type code; CX.4 is the assigning authority. Both must be populated to disambiguate identifiers across systems. Engines should warn on missing CX.4 for any code in (MR, PI, NPI, NPN).
• Case sensitivity — HL70203 codes are case-sensitive uppercase. Normalize on ingest.
• Local code registry — Maintain a per-site registry of locally-extended HL70203 codes with documentation, FHIR system URIs, and intended FHIR Identifier.type.coding bindings.

How Vorro handles HL70203

Vorro validates CX.5 against the full HL70203 set plus the site's locally-extended codes on ingest. Unrecognized values are routed to the terminology curation queue rather than silently passed; once curated, the new code joins the site's registry and is honored on all future messages.

On FHIR outbound, Vorro emits Identifier.type.coding with the HL70203 system URI and the original code. For codes with a known FHIR-narrowed equivalent (e.g., MR → FHIR MR), the additional FHIR coding is added as a second entry in Identifier.type.coding so consumers bound to the narrower value set still resolve a match.

Related pages

• CX data type — Extended Composite ID with Check Digit
• PID segment — Patient Identification
• HL70363 code table — Assigning Authority

Sources

• HL7 Terminology — CodeSystem v2-0203 Identifier Type
• HL7 v2 product brief