Functional Groups, often referred to as the “inner envelope,” are made up of one or more Transaction Sets, all of the same type, which can be batched together into one transmission. The Functional Group is defined by the header and trailer segments.
The Functional Group Header (designated GS) segment appears at the beginning, and the Functional Group Trailer (designated GE) segment appears at the end. Many Transaction Sets can be included in the Functional Group, but all local transactions must be of the same type.
Within the Functional Group, each Transaction Set is assigned a functional identifier code, which is the first data element of the header segment. The Transaction Sets that constitute a specific Functional Group are identified by this functional ID code.
The GS segment contains:
Functional ID code (the two-letter transaction code; for example, PO for an 850 Purchase Order, HS for a 270 Eligibility, Coverage, or Benefit Inquiry) to indicate the type of transaction in the Functional Group
Identification of sender and receiver
Control information (the Functional Group control numbers in the header and trailer segments must be identical)
Date and time
The GE segment contains:
Number of Transaction Sets included
Group control number (originated and maintained by the sender)