IEA
Interchange Control Trailer. The closing segment of the ISA envelope — it counts the included groups and echoes the control number.
Definition
In the ANSI ASC X12.5 standard, IEA is the mandatory closing segment of an X12 interchange. It performs two structural checks:
- IEA01 — Number of Included Functional Groups (element I16): count of GS/GE pairs between ISA and IEA. The receiver verifies this counter matches the actual count.
- IEA02 — Interchange Control Number (element I12): control number, identical to ISA13 of the opening ISA. Helps detect orphan fragments and truncated transmissions.
Origin
The ISA/IEA pair has been defined in X12 since version 002001 (1985). Its purpose is purely syntactic — IEA carries no business data, it serves exclusively to verify that the interchange arrived intact and that its control number is consistent. Maintained by ASC X12 under the X12.5 Interchange Control Structures standard.
Example in context
End of interchange with a single functional group and control number 000012345:
Reading: one functional group (1), interchange control
number 000012345 echoed from ISA13. Any difference triggers
a structural rejection or a negative TA1.