Obtaining replacement keys for BMW vehicles made after 1995 requires contacting a BMW dealer. Keys for these vehicles are coded uniquely to each vehicle for security, so it is necessary for a dealer to reprogram a new key to match the code of a specific vehicle.
As of 2015, BMW cars use the company's electronic immobilizer technology, which uses a rotating code system that is updated each time a key is used in the car. The immobilizer verifies both that the key is coded to the car itself and that the rotating code matches the last rotating code uploaded to that key before allowing the engine to start. Unless both codes match, it is not possible to start the engine.
Replacing a lost BMW key can be expensive, depending on the model of the car. It is possible to obtain blank BMW keys from used parts dealers, and some software manufacturers claim to have products that allow individuals to sync blank BMW keys to a car. The efficacy of this kind of software is not guaranteed, however, and there may be potential warranty or legal ramifications from its use. BMW may also change the keying scheme in future cars to render these types of programs ineffective on new models.