How to Know If You Have a Bad ESN

by Andy Warycka

Buying a used cell phone can save you a lot of money if you're looking for an upgrade or a replacement, but if you don't do your homework before handing over the cash, a phone with a bad ESN can leave you with an expensive plastic brick. With a little help from the seller, it's possible to verify the status of an ESN before you ever spend any money, saving you money and a major headache.

The ESN Defined

The ESN, or electronic serial number, is a unique number that identifies a particular mobile device to a wireless carrier. An MEID, or Mobile Equipment Identifier, serves the same purpose. When a call is made, the phone transmits the ESN or MEID over the cellular network so the carrier can verify the validity of the call. This number is printed on the label under the battery or on the back of the phone, printed on the chip inside the phone, and embedded in the phone's memory and cannot be easily -- or, for that matter, legally -- changed. Not all phones and carriers use the embedded phone ESN to identify the phone on the network: only those using CDMA technology like Verizon and Sprint in the United States do so. GSM phones with SIM cards use a different identification scheme.

Bad ESN Causes

The most common cause of a bad ESN is an unpaid balance on the phone's account. This can be from a customer who didn't pay their final bill, one who switched carriers and didn't pay the early termination fee or someone who simply stopped paying and let the service lapse. A bad ESN is also caused by the phone being reported lost or stolen to the carrier.

Checking an ESN

Once you have obtained the ESN, you can check the status of the phone in one of two ways. You can call the carrier on which the phone was last used and simply ask them to verify whether the ESN is clear or not. If it is bad, they may be able to provide you with the reason as well. You can also go to CheckESNFree on the Web (link in Resources) where you can select the carrier, enter the ESN of the phone and the service will tell you instantly whether the ESN is good or bad.

Fixing a Bad ESN

Unfortunately, carriers will not allow you to pay off debts associated with a phone that isn't yours -- assuming you'd want to in the first place -- and stolen or lost phones cannot be activated, either. The only remaining options are to have the phone "flashed" to work on another carrier or to sell the phone for parts to attempt to recover any losses from the purchase price.

About the Author

Andy Warycka has been writing professionally since 2009. His work has appeared on sites such as,, and other top online properties. He owns a photography business, and holds an Associate of Applied Science in photography from the Rochester Institute of Technology.

Photo Credits

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