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Spotlight PEPPOL BIS Billing 3.0 The EU e-invoicing mandate is here — France Sept 2026, Belgium Jan 2026, Germany 2025.

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ISA

Interchange Control Header. The outer envelope of every X12 interchange — identities, version, separators, control number, test/prod indicator.

Definition

In the ANSI ASC X12.5 standard, ISA is the only X12 segment with a fixed length (106 characters). It mandatorily opens every interchange and carries 16 elements:

  • ISA01-02 — Authorization Information Qualifier & Information: 00 No authorization information present + 10 spaces, or a mutually agreed authentication mechanism.
  • ISA03-04 — Security Information: same logic for password.
  • ISA05 — Interchange ID Qualifier (Sender): 01 DUNS, 14 DUNS+4, ZZ Mutually defined.
  • ISA06 — Interchange Sender ID: sender identifier (15 characters).
  • ISA07-08 — Interchange ID Qualifier & Receiver ID: for the receiver.
  • ISA09 — Interchange Date (YYMMDD), ISA10 — Time (HHMM).
  • ISA11 — Repetition Separator (from version 00501) or Interchange Control Standards Identifier (earlier versions).
  • ISA12 — Interchange Control Version Number: 00501, 00401, etc.
  • ISA13 — Interchange Control Number: 9 digits, echoed in IEA02.
  • ISA14 — Acknowledgment Requested: 0 No / 1 Yes (TA1).
  • ISA15 — Usage Indicator: P Production, T Test, I Information.
  • ISA16 — Component Element Separator: the character separating components of a composite element.

Origin

ISA has been in X12 since version 002001 (1985). Its uniqueness — fixed length — comes from the fact that it also serves as a separator discovery mechanism (Element Separator, Segment Terminator, Component Element Separator). The X12 parser reads the 106 characters blind and derives the separators from positions fixed by the standard. Standard maintained by Accredited Standards Committee X12 under X12.5.

Example in context

Reading: no authentication (ISA01-04), mutually defined sender ACME, receiver BUYER, 14 May 2026 at 15:30, version 00501, control 000012345, no TA1 requested (0), production (P), component separator >.

  • IEA — the symmetric interchange closer.
  • GS — the business sub-envelope.
  • DUNS — the typical identifier used in ISA05-08.

Last updated: May 14, 2026