IMEI, otherwise known as International Mobile Equipment Identification, is a series of numbers that identifies key elements of the phone that it can be registered to a single user and reported stolen if necessary. This IMEI is also used for identification in phone tracing methods and terrorist activities identification. This number is printed or etched onto the phone behind the battery so that it may be found when necessary.
The information that the IMEI is able to store on the phone is amazing. Not only is each number different, but each number can explain the origin of the phone, the model, and the serial number. This can come in handy if the phone is stolen or if the phone needs to be used as evidence for any legal action. The original purpose of this IMEI number was so that if the phone were to get stolen, the phone owner could call the network provider and have the phone blocked so that it could not be used with any provider.
This purpose has been expanded to cover phone identification for legal processes. In addition to the IMEI being located behind or under the battery, one can locate the number on the phone. For those new phones, one simply has to dial the phone and wait for it to answer. For phones that have been refurbished, one should check to see if the number the phone gives verses the engraved number are the same and should contact your provider if not. If the IMEI numbers between the phone and the engraving do not match, one should call their provider and ensure that it is not going to cause problems later for them.
Because the IMEI is the identification number of the phone and is often used to deter phone theft, it is illegal in many places to own the equipment or to perform the act of physically changing the IMEI on a phone. The act of or the ability to change the IMEI on a phone would make it possible to use a stolen phone that has been banned by the phone service providers. This then encourages theft and makes it difficult to track the phone. In some cases, this can be punishable in a court of law.
To guard against the purposeful changing of the numbers and the incorrect entry of an IMEI number, the phone companies have created a check number that can be derived from the numbers in the IMEI. This number helps by making it impossible for an individual to change then numbers without upsetting the charge mouth.
Tyler Bain writes on topics such as What is IMEI?, How can I Find my IMEI? and What is a Subscriber Identity Module (SIM)? for The Tech FAQ.