How to Know if an IMEI Is Cleanby John Lister
An International Mobile Equipment Identity number is one of the main identification codes for individual cell phone handsets. Many cell phone networks will check a phone's IMEI before allowing it to connect to the network; the network can then block communication with blacklisted handsets, thus making it useless. Note that the IMEI is different to either the handset's telephone number or an identification number for a SIM card, neither of which is necessarily permanently linked to the handset in the same way as an IMEI.
You can use one of three main methods for finding a handset's IMEI number. One is through the Settings menu on the phone itself: the precise instructions for accessing the IMEI this way depend on the phone. A second is to remove the battery from your phone (which isn't possible on all models) and look for a label with the details. A third option, which usually only works with non-smartphones with a physical keyboard, is to type in "*#06#" (minus the quotation marks) and the phone displays the IMEI number.
After you have an IMEI number for a handset, the official way to check is to contact the carrier to which the phone is currently registered and ask it to check. You may find some carriers will not do so unless you are a current customer. As of September 2013, you can check on T-Mobile's website (see Resources) regardless of which network you use or to which network the phone is registered. You can also use independent websites such as Swappa, IMEI Info or IUnlocker (see Resources). In the U.S. at least, all networks use the same database, so using any checking service should tell you if a phone is blocked. You should not need to pay anyone to check an IMEI number.
If an IMEI is blacklisted, the phone has been reported as stolen. If you are checking the status of a potential purchase and it appears on the blacklist, do not buy it as you are highly unlikely to be able to use it. If you already own the phone, you can try contacting the seller and asking him to resolve the problem or refund your purchase. Normally only the person who owned the phone at the time its IMEI was blocked can get the block lifted.
Phones registered to Sprint and Verizon, as well as some smaller networks, use an alternative identification number. This is an MEID (mobile equipment identifier) number. It can be made up of a mix of letters and numbers (MEID HEX) or a string of numbers only (MEID DEC). The general principles of the system and checking work in a similar way to IMEI.