Car key replacement

What the job covers

• Cutting and programming a spare transponder key from a working one
• Replacing a lost or stolen key and deleting it from the immobiliser
• A new remote fob or keyless proximity key programmed to the car
• Moving the chip and blade into a new case when a fob has broken
• Repairing worn buttons or a loose battery contact on a remote key

Replacing a car key means making two things match: the blade has to turn the locks, and the electronics have to be accepted by the car. Most cars built since the late 1990s carry a transponder chip in the key, and the engine will not start unless the immobiliser recognises it.

Keys come in four broad kinds. A plain cut key on an older car needs cutting only. A transponder key is cut and then programmed to the car. A remote fob adds buttons for the central locking, which are paired as well. A keyless or proximity key lets the car unlock and start with the key in a pocket, and is the most involved to replace. Some blades are laser-cut, with a groove along the face rather than teeth on the edge, and need a different cutting machine.

A spare from a working key is the simplest job: the locksmith reads the existing key and adds a new one. All keys lost is harder, because there is nothing to copy. The locksmith decodes the lock or uses the car's data to cut a key, programmes it, and should delete the lost keys from the immobiliser's memory so they no longer start the car. That deletion is worth asking for whenever a key has been stolen.

For some makes the programming needs manufacturer data. Since 1 April 2026 that data comes through UK SERMI for Ford, Jaguar, Land Rover, Nissan and Toyota, and a locksmith without access may have to refer the job to a dealer. A broken fob case, by contrast, can often be fixed by moving the chip and blade into a new shell. Whatever the job, a careful auto locksmith asks for the V5C logbook and photo ID before cutting anything.

Ask for the total before anyone sets off: the key, cutting, programming, any call-out charge and VAT. Give the make, model, year and registration, and say whether you still have a working key. Ask whether they can programme that make themselves or need manufacturer data through UK SERMI, and whether the key is an original part or an aftermarket one. If a key was lost or stolen, ask them to delete it from the immobiliser. Have the V5C logbook and photo ID ready; a careful auto locksmith asks for both before cutting a key, and will not make one without them.

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