The number is composed of the following subparts:
- Issuer Identification Number (IIN) - Maximum of seven digits:
- Issuer identifier, 1–4 digits.
- Individual account identification - length is variable, but every number under one IIN will have the same length.
- Check digit - Single digit calculated from the other digits using the Luhn Algorithm.
In practice, this means that on GSM SIM cards there are 20-digit (19+1) and 19-digit (18+1) Integrated Circuit Card Identifiers in use, depending upon the issuer. However, a single issuer always uses the same size for its ICCIDs.
To confuse matters more, SIM factories seem to have varying ways of delivering electronic copies of SIM personalization datasets. Some datasets are without the ICCID checksum digit, others are with the digit.
The most recent list, as of November 2013, is in Operational Bulletin No. 1040.
More Information#There might be more information for this subject on one of the following:
- Issuer Identification Number
- Major Industry Identifier
- Mobile Station International Subscriber Directory Number