Interchange Control Number
X12 envelope control number matched between ISA13 and IEA02.
Definition
The sender assigns a control number in ISA13 (data element I12, exactly 9 numeric digits, typically incremented per interchange). The same value must reappear in IEA02; a mismatch is an envelope error reported by TA1. Receivers commonly use it for duplicate-interchange detection, so resending the same number with new content is a known reconciliation pitfall.
Origin
Defined as data element I12 (Interchange Control Number) in the ANSI ASC X12.5 interchange envelope, maintained by the Accredited Standards Committee X12. Its echo in IEA02 (element I12 again) provides the open/close integrity check.
Example in context
<ISA*...*000012345*0*P*>~ ... <IEA*1*000012345~ — interchange numbered 000012345, the same value closing the envelope in IEA02.</p>