There is an implicit relationship between Field 42 – Merchant ID code and Field 41 – Card Acceptor Terminal Identification (also known as Terminal ID Code) in Elavon’s ISO 8583 protocol.
If a Merchant ID code is, for example, 123456789, then related terminal IDs will be 12345678901, 12345678902, 12345678903 etc.
The eight digit Terminal ID in Field 41 should be sent as 00000001, 00000002, 00000003, etc.
The TID will be generated and provided by Elavon to the customer.
Alphanumeric Terminal IDs
The use of an alphanumeric terminal ID is possible but only permitted under special circumstances. Alphanumeric TIDs should be populated as follows:
Field 41 (Card Acceptor Terminal Identification) is zero filled.
Field 63, Tag 05 (Ignore TID Indicator) is set to ‘Y’.
Field 63, Tag 20 (Alphanumeric Terminal ID) carries the required terminal ID number.