Section title: Requests for Interpretation
Must X12 documents be processed in order of ICN (Interchange Control Number)?

Is it mandatory that documents received be processed in order of ICN value? Or any other value (timestamp, etc.) to ensure that transaction sets are acted upon in serial order?


We have a trading partner who we transmit files to containing different transaction sets that operate on the same logical entity. These transaction sets have business rules that require them to be applied in a specific order. Specifically, in this case we have a 855 and then an 856 that needs to be processed in that order (855 before the 856). We are providing them with two files, one containing each of these documents. They are processing both of the files as they receive them, however they are not guaranteeing completion of lower ICN numbers or any kind of sequential processing, and thus have a race condition in which they attempt to process the 856 with a higher ICN number than the 855 file.

We would like to understand if it is part of the X12 specification that when processing X12 documents, one must respect ICN number and process in a serial fashion or not.

RFI Response

*X12.5 Interchange Control Structures defines ‘control structures for the electronic interchange of one or more encoded business transactions’.

* Section 3.2.1 defines the basic interchange service request performs various functions, including ‘Provides control information for the interchange’.  Additionally, Section 4.1 states that ‘the control segment is used primarily to convey control information and to group data segments’.

* I12 Interchange Control Number is defined as a control number assigned by the interchange sender

and restricted to use in interchange control structures.

* X12.59 Implementation of EDI Structures, Section 5.1 Interchanges within a Logical Communications Exchange, states ‘Each instance of a logical communications exchange shall be considered to be an external, enveloping structure of the interchanges that are transferred within that session.

Therefore, the ICN does not pertain to nor guides the sequence of transaction processing by the EDI parties.

Any transaction processing requirements require a separate agreement between the parties.