Number Structure
Currently, the IMEI structure is as follows:
| TAC - Type Allocation Code | Serial Number | Check Digit | |
| NN | XXXXXX | ZZZZZZ | A |
| Reporting Body Identifier, eg BABT (35) | Type Identifier defined by BABT | Number range allocated by BABT but assigned to individual mobile stations by the manufacturer. | Defined as a function of all other digits (calculated by the manufacturer). |
The TAC number (the first 8 digits) allocated by the Reporting Body plus the serial number (6 digits) assigned by the TAC holder gives 14 digits of the 15 digit IMEI number.
The fifteenth digit is the Check Digit. This is calculated from the other fourteen digits by the TAC holder using the Luhn formula. An example of the calculation is given in 3GPP specification TS 23.003.
TAC numbers allocated by BABT usually begin 35. However, products that include dual mode 3GPP/3GPP2 (CDMA2000) technologies, as of 13th February 2009 are allocated a TAC number beginning 98.
| BABT's IMEI Number Allocation Pages | |
