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Back  RFI # 723: Control Numbers in Interchange

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Carter DeMan


Independent of how and when communicated, in multiple interchanges from one trading partner to another, must the sender-assigned interchange control number (ISA13 and IEA02) value always be unique for each interchange ...forever?

Submitter Assigned Keywords

unique control numbers


The X12 standard (X12.5, Section 5.1.2, paragraph 3) states:

“In order to provide sufficient discrimination for the acknowledgment process to operate reliably and to ensure that audit trails are unambiguous, the combination of interchange sender’s qualifier and ID (ISA05, ISA06), interchange receiver’s qualifier and ID (ISA07, ISA08) and the interchange control number value (ISA13) shall by themselves be unique within a reasonably extended time frame whose boundaries shall be defined by trading partner agreement. Because at some point it may be necessary to reuse a sequence of control numbers, the Interchange Date and Time may serve as an additional discriminant only to differentiate interchange identity over the longest possible time frame.”

In summary, no, the sender-assigned interchange control number (ISA13 and IEA02) value is not required to be unique for each interchange forever.


Under normal EDI procedures the number would be incremented in some fashion and would not repeat until the max number has been reached. The only requirements would fall within trading partner agreements and processes.
Submission 1/12/2009
Status Date 8/28/2009
Status F - Final
Primary References
Document all
Set IDall
Segment IDISA
Element Position13
Industry NameInterchange Control Number
Secondary References
RFI ID 646
Document all
Set IDall
Segment IDIEA
Element Position02
Industry NameInterchange Control Number