HL7 ACK & error code lookup

Acknowledgment codes (MSA-1), v2 error conditions (ERR-3, Table 0357) and FHIR OperationOutcome issue types, with what to check first.

Acknowledgment codes (Table 0008)

Code	Meaning	What to check
AA	The receiving application accepted the message for processing. In original mode this is success; in enhanced mode this is the application-level accept.	Check MSA-2 matches your MSH-10. AA is not a promise every downstream system stored the data — only that this app accepted it.
AE	The application understood the message but found an error (validation, business rule, missing data). Often paired with ERR.	Read ERR-3 (table 0357) and ERR-8. Fix the field or the feed mapping; do not invent identifiers.
AR	The application rejected the message before/without successful application processing — unsupported type, bad encoding, missing control ID, wrong processing ID, etc.	Check MSH-9/10/11/12 and whether this receiver even supports the trigger.
CA	Enhanced mode only: the commit (accept) acknowledgment — the receiver safely stored the message for later application processing.	You may still get a later application ACK (AA/AE/AR) depending on MSH-15/16.
CE	Enhanced mode: commit-level error — the receiver could not accept responsibility for the message (storage/protocol problem).	Retry policy depends on your interface contract; inspect ERR if present.
CR	Enhanced mode: commit-level reject — the receiver will not accept this message at the commit layer.	Usually a protocol/config mismatch, not a soft validation issue.

Message error conditions (Table 0357)

Code	Meaning	What to check
0	Message accepted — Success detail code some systems return alongside AA.	Optional; AA already means accept.
100	Segment sequence error — Segments out of order or a required segment missing.	Compare the message structure to the profile (e.g. ADT_A01).
101	Required field missing — A required field is empty.	Penford example: empty PID-3 MRN → ask registration, then edit & resend with a confirmed value.
102	Data type error — Wrong datatype (NM field contains FOO).	Check OBX-2 vs OBX-5; dates must be DTM.
103	Table value not found — ID/IS value not in the expected table.	Map with a code table (and a * default) instead of forcing a wrong code.
104	Value too long — Exceeded normative or app-safe length.	Truncate only if the contract allows; otherwise fix the source.
200	Unsupported message type — Receiver does not support MSH-9.1.	Add a destination filter; do not coerce the type.
201	Unsupported event code — Trigger in MSH-9.2 not supported.	Filter A40 merges away from systems that cannot merge.
202	Unsupported processing id — MSH-11 not accepted (often TEST vs PROD).	Fix the connection environment; do not rewrite MSH-11 to sneak it in.
203	Unsupported version id — MSH-12 version not supported.	Align versions or use a version-tolerant engine path.
204	Unknown key identifier — Referenced patient/order id was not found.	For merges, ensure the prior MRN was registered first.
205	Duplicate key identifier — Id already exists on an add-style transaction.	Check whether this should have been an update trigger.
206	Application record locked — App storage locked.	Retry later; usually transient.
207	Application internal error — Catch-all application error — detail often in ERR-5.	Read ERR-5/7/8 before resubmitting the same bytes.

FHIR OperationOutcome issue types

Code	Meaning	What to check
invalid	Invalid Content — Content failed the specification or profile.	Validate against the IG (e.g. US Core) before retrying.
structure	Structural Issue — JSON/XML could not be parsed or structure is wrong.	Check resourceType and required nesting.
required	Required element missing — A required element is absent.	Penford example: Patient.identifier missing when the IG requires it.
value	Element value invalid — A value is present but not acceptable.	birthDate needs YYYY-MM-DD, not YYYYMMDD.
invariant	Validation rule failed — A FHIRPath/invariant (or similar) failed.	Read OperationOutcome.diagnostics.
not-supported	Content not supported — Interaction, resource, or profile not supported.	Check CapabilityStatement.
duplicate	Duplicate — Create would duplicate an existing record.	Search by identifier before create.
not-found	Not Found — Reference target missing (HTTP 404 analogue).	Confirm the id on that server.
code-invalid	Invalid Code — Code/system not understood or not in ValueSet.	Fix Coding.system URI (LOINC, SNOMED).
business-rule	Business Rule Violation — Failed a business rule beyond schema.	Talk to the owning system — mapping alone may not fix it.
conflict	Edit Version Conflict — Version-aware update conflict (HTTP 409 analogue).	GET latest meta.versionId, then retry.
transient	Transient Issue — May succeed if retried later.	Use retry with backoff; do not “fix” identifiers.
exception	Exception — Unexpected internal error.	Capture issue.diagnostics for the server team.
informational	Informational Note — Note unrelated to hard failure.	Do not treat as error unless severity says so.

Sources: HL7 Table 0008 · HL7 Table 0357 · FHIR R4 issue-type. Related: MSA · ERR