Structure of the IMEI and IMEISV

The IMEI (14 digits plus check digit) or IMEISV (16 digits) includes information on the origin, model, and serial number of the device. The structure of the IMEI/SV are specified in 3GPP TS 23.003. The model and origin comprise the initial 8-digit portion of the IMEI/SV, known as the Type Allocation Code (TAC). The remainder of the IMEI is manufacturer-defined, with a Luhn check digit at the end (which is never transmitted).

As of 2004, the format of the IMEI is AA-BBBBBB-CCCCCC-D, although it may not always be displayed this way. The IMEISV drops the Luhn check digit in favour of an additional 2 digits for the Software Version Number (SVN) in the format AA-BBBBBB-CCCCCC-EE

Prior to 2002, the TAC was 6 digits long and followed by a two-digit Final Assembly Code (FAC), which was a manufacturer-specific code indicating the location of the device's construction.

For example the IMEI code 35-209900-176148-1 or IMEISV code 35-209900-176148-23 tells us the following:

TAC: 352099 so it was issued by the BABT and has the allocation number 2099

FAC: 00 so it was numbered during the transition phase from the old format to the new format (described below)

SNR: 176148 - uniquely identifying a unit of this model

CD: 1 so it is a GSM Phase 2 or higher

SVN: 23 - The 'software version number' identifying the revision of the software installed on the phone. 99 is reserved.

The format changed from April 1, 2004 when the Final Assembly Code ceased to exist and the Type Approval Code increases to eight digits in length and became known as the Type Allocation Code. From January 1, 2003 until this time the FAC for all phones was 00.

The Reporting Body Identifier is allocated by the Global Decimal Administrator; the first two digits must be decimal (ie less than 0xA0) for it to be an IMEI and not an MEID.

The new CDMA Mobile Equipment Identifier (MEID) uses the same basic format as the IMEI.