EDI X12 Structure: Interchange Control Header (ISA)

EDI X12 Structure will be analyzed on the the EDI 850 example document (Purchase Order). This particular EDI file contains two purchase orders from a retailer to a supplier, sent on 11/01/2005. Now you see why EDI transactions are primarily handled by computers. But with a little practice after our webinars you’ll soon learn to decipher an EDI transaction.

Reading an EDI transaction begins by knowing that each line (properly referred to as a segment) starts with a code that tells you something about the information on that line, and each line has a matching pair item that marks the end of that level of information. A functional group header has a functional group trailer; an interchange control header has an interchange control trailer.

EDI X12 Structure

On the image above, you will see what these letter codes mean and as we progress, you will learn more about each type of information. For now, just understand that each of these is a carefully agreed upon, completely standardized means of transmitting some portion of the information that is important to the particular transaction—in this case, the purchase order.

Within each segment, various kinds of information appear, each separated by an asterisk or other identifier. In discussing EDI information, we refer to a particular line by its letter/number name and then to the specific position within that line. So, “ISA 1 through 4” is the ISA line, positions 1 through 4. Each position is set of by (generally) asterisks.

Interchange Control Header (ISA)

This is the beginning segment of almost all EDI documents. This is the outermost envelope, all of the EDI data is placed within this layer. The purpose of this segment is to identify the sender and receiver, date, time and control number information. This segment must match the IEA trailer segment.

ISA*00* *00* *12*6194537845 *12*8997372426 *051101*0306*U*00401*100000799*0*P*>

ISA-01 through ISA-04: In the example above, ISA-01 through ISA-04 are hardly ever being used anymore and that is why they are 00 and blank. They served authorization and security password purposes in the past.

ISA-05 and ISA-06: These segments represent the sender qualifier and the sender ID. In the example above ISA-05 has a qualifier of 12 which means the phone number and ISA-06 has the actual phone number.

ISA-07 and ISA-08: These segments represent the receiver qualifier and the receiver ID. In the example above ISA-05 has a qualifier of 12 which means the phone number and ISA-06 has the actual phone number.

ISA-09 and ISA-10: ISA-09 is the interchange date in YYMMDD format. ISA-10 is the time in HHMM format. In the example above this document was sent on November, 1st 2005 at 03:06 AM.

ISA-11: For EDI Versions (see ISA-12) 00402 and greater this will serve as a repetition separator used to separate repeated occurrences of a simple data element or a composite data structure. For example a pipe character (I) or a carrot (“^”) can be used in this field. For EDI versions 00401 or less (like in our
example above) this will always be will be a single character code value “U” meaning “U.S. EDI Community of ASC X12, TDCC, and UCS”. Some companies will still send “U” in versions greater than 00402. Most EDI translators are smart enough to figure out if they encounter a “U” (or probably any other alpha or numeric character) in ISA11 (regardless of version), they presume it is the old ISA version value and not the repetition separator.

Conversely, when they encounter a symbol such as a carrot (“^”), they presume it is the new ISA version value which is the repetition separator. More on repeating and composite data element structures will be discussed later in this course.

ISA-12: This is the EDI standard published version number. In the example above it is 00401; Standards Approved for Publication by ASC X12 Procedures Review Board through October 1997 ISA-13: This is a 9 digit control number used for tracking purposes. This number must match IEA-02 (Interchange Envelope Trailer). This number should be unique and should not be re-used for at least 3 years.

ISA-14: This is hardly ever used and should not be confused with the 997 acknowledgement document. This is the acknowledgement request indicator for the TA1 transaction and is used mainly for reporting the status of processing a received interchange header and trailer or the non-delivery by a network provider. Most of the time this will be set to ‘0’.

ISA-15: This indicates whether data enclosed by this interchange envelope is test ‘T’, production ‘P’ or information ‘I’. In the example above it is ‘P’ ISA-16: This field provides the delimiter used to separate component data elements within a composite data structure; this value must be different than the data element separator and the segment terminator. In the example above the value is the “greater than” (>), however, it can also be any valid ASCII special character. This is also referred to as the Sub-Element Separator.

To learn more about EDI mapping and become a certified  EDI Professional please visit our course schedule page.

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