Overview#Type Allocation Code (TAC) is the initial eight-digit portion of the 15-digit IMEI and 16-digit IMEISV codes used to uniquely identify Mobile Devices.
January 1, 2003 Changes#Prior to January 1, 2003, the global standard for the IMEI started with a six-digit Type Approval Code followed by a two-digit Final Assembly Code (FAC). The Type Approval Code (also known as TAC) indicated that the particular device was approved by a national GSM approval body and the FAC identified the company that had built and assembled the device (which is not always the same as the brand name stamped on the device).
Effective January 1, 2003, many GSM member nations and entities (mainly Europe) moved away from requiring that devices be approved by national bodies, and towards a system where device manufacturers self-regulate the device market. As a result, a manufacturer now simply requests an eight-digit Type Allocation Code for a new phone model from the international GSM standards body, instead of submitting a device for approval to a national review body.
Both the old and new Type Allocation Code uniquely identify a model of phone, although some models may have more than one code, depending on revision, manufacturing location, and other factors.