SWIFT MT Message Block 1 (Basic Header) Description

July 25, 2021
Category: SWIFT MT

The description of the SWIFT MT Message Block 1 (Basic Header) is provided in the table below. For the sake of clarity, following elements have been added: Start of block indicator, Block identifier, Separator and End of block indicator. There are in general not part of block descriptions in the available documentation. But I think it can be useful.  Back to SWIFT MT Message structure page with links to the other blocks.

Tag or field name M / O Description and Semantic Content / Options Example
Start of block indicator M The character { indicates the beginning of a block. Left curly bracket { {
Block identifier M 1 to 3 alphanumeric characters used to define block contents. Basic header block identiifer is 1. 3c 1
Start of block indicator M The character { indicates the beginning of a block. Left curly bracket { {
1 AppID M The Application Identifier identifies the application within which the message is being sent or received. The available options are: F = FIN All user-to-user, FIN system and FIN service messages A = GPA (General Purpose Application) Most GPA system and service messages L = GPA Certain GPA service messages, for example, LOGIN, LAKs, ABORT These values are automatically assigned by the SWIFT system and the user's CBT 1a F
2 ServiceID M The Service Identifier consists of two numeric characters. It identifies the type of data that is being sent or received and, in doing so, whether the message which follows is one of the following: a user-to-user message, a system message, a service message, for example, a session control command, such as SELECT, or a logical acknowledgment, such as ACK/SAK/UAK. Possible values are 01 = FIN/GPA or 21 = ACK/NAK. 2n 01
3 LTAddress M The Logical Termial (LT) Address is a 12-character FIN address. It is the address of the sending LT for input messages or of the receiving LT for output messages, and includes the Branch Code. It consists of: - the BIC 8 CODE (8 characters) - the Logical Terminal Code (1 upper case alphabetic character) - the BIC Branch Code (3 characters) 12x BANKFRPPAXXX
4 SessionNumber The Session Number identifies the session in which the message was transmitted. It is a four digits number that is automatically generated by the user's computer and padded with zeros. 4n 4321
5 Sequence Number (ISN or OSN) M The sequence number always consists of six digits. It is the Input Sequence Number (ISN) of the sender's current input session or the Output Sequence Number (OSN) of the receiver's current output session. It is automatically generated by the user's computer and padded with zeros. 6n 123456
End of block indicator M The Block identifier end tag Right curly bracket } }

Example of Basic header block
{1:F01BANKFRPPAABC4321123456}
{1:F 01 BANKFRPPAABC 4321 123456} with spaces between the fields

Back to SWIFT MT Message structure page with links to the other blocks.