How immobilisers impact car insurance

Your car's security can have an important impact on your insurance premiums; here's how immobilisers fit into your vehicle's security suite.

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If your car was made from 1998 onwards, it almost certainly has a security device known as an electronic immobiliser installed. Not only can an immobiliser reduce the risk of theft, it can also help keep your car insurance premiums down. Read on to find out how immobilisers work and why owners of older cars might want to think about getting one.

What is an immobiliser?

An immobiliser is a device that forms part of your car’s security. It is designed to prevent anyone from driving your car away without the correct key or fob. As such, it helps prevent criminals from stealing your car.

What are the different types of immobiliser?

There are a few types of car immobiliser:

  • Mechanical immobilisers. These are a fairly basic form of immobiliser that you can buy to use on any car. Common types of mechanical immobiliser include steering wheel locks, which prevent your steering wheel from being turned even if someone is able to start the car, and wheel clamps, which can be fastened around your tyres. Parking authorities often use wheel clamps to prevent your car from being moved if it’s illegally parked, but individuals can also buy them as a security device.
  • Built-in electronic immobilisers. These are built into your car’s ECU (Electronic Control Unit), and prevent your car from starting if a fake key is used in the ignition, or if a thief tries to hotwire your car. They’ve been compulsory for manufacturers to install in new cars since 1998 (known as “factory-fitted” immobilisers).
  • Ghost immobilisers. This is one of the newest forms of immobiliser. You have to proactively enter a passcode sequence, using the existing buttons in your car, before your car will start.

How do electronic car immobilisers work?

The exact details of how immobilisers work isn’t widely publicised, for obvious security reasons. But at a top level, a car immobiliser typically disables 2 or 3 components of your car: the fuel system, the starter motor, and/or the ignition.

When you use the correct key or fob, it sends a digital code to your car’s ECU. This will then enable the disabled elements and allow your vehicle to start. If a thief tries to use an incorrect key, or tries to hotwire your car, your ECU won’t receive the correct code and the car shouldn’t start.

How do I know if my car has an electronic immobiliser?

It became compulsory for car manufacturers to factory-fit immobilisers into cars on 1 October 1998. So, if your car was made since then, you can feel pretty confident that it has an immobiliser.

Immobilisers have been around a bit longer than this though – since 1992 to be specific. So some pre-1998 cars may have immobilisers that the manufacturer fitted voluntarily. If so, it should be specified in your car’s handbook. You can also try contacting your car’s manufacturer. Other older cars may have had then retrospectively installed. If you have a second-hand car and you’re not sure if it has an immobiliser or not, you can ask a mechanic to check.

What is a Thatcham device?

Thatcham is an independent vehicle security firm. The services it offers include rating the security of devices intended to keep cars secure, such as immobilisers and alarms.

It has a number of different categories of car security, with Class 1 offering the most robust security. Immobilisers and other security devices that are “Thatcham approved” have been assessed by Thatcham and deemed to have met the criteria for that category of product.

Insurers tend to favour security devices that are Thatcham approved. When you fill in a car insurance application form, you will usually be asked if any devices you have fitted are Thatcham approved.

  • Category 1 – Alarm and electronic immobiliser
  • Category 2 – Electronic immobiliser
  • Class 2-1 – Alarm upgrade (where you add a Thatcham-improved alarm to an existing Category 2 immobiliser)
  • Category 4 – Locking wheel devices
  • Category S5 –Vehicle tracking systems
  • Category S7 – Asset location systems (devices that increase the probability of the recovery of a stolen asset)

How do ghost immobilisers work?

Ghost immobilisers are a more recent innovation than electronic immobilisers, so you’re unlikely to find them built in by the manufacturer. You can add one into a car with an existing electronic immobiliser.

As with electronic immobilisers, a small, discreet device is installed in your car. But it’s not linked to your car key or fob. Instead you set a passcode sequence using the buttons in your car, such as those on the steering wheel, door panels or centre console.

Without putting in the correct passcode, it won’t be possible to start the vehicle.

Can I fit an electronic immobiliser into an older car?

Yes. If your car was made before 1998 and doesn’t have a factory-fitted immobiliser, then you can get one fitted retrospectively. You’ll need a mechanic to fit it for you. We’d recommend getting a Thatcham approved one. That’s not only because you’ll have the reassurance that it’s passed independent assessments, but also because insurers are more likely to recognise Thatcham approved devices and offer you a discount on your premiums.

How much does installing car immobiliser cost?

If you have an older car without a factory-fitted immobiliser, and want to fit one – or to upgrade to a ghost immobiliser – expect to pay between around £250 and £600. The cost will depend on the specific features and levels of security. Ghost immobilisers tend to sit at the higher end of the price spectrum.

Will an immobiliser reduce my car insurance premiums?

Danny Butler

Finder insurance expert Danny Butler answers

Car insurers are a fan of anything that will reduce the risk of you having to make a claim and therefore costing them money. Immobilisers are one of a number of security measures that can reduce the risk of your car being stolen. As such, a car with an immobiliser installed is likely to cost less to insure than an otherwise identical car without an immobiliser.

If you have a modern car, insurers will usually assume when they give a quote that your car has a factory-installed immobiliser. You’ll need to actively correct this assumption if, for whatever reason, the immobiliser has been removed. And you’ll need to actively tell them if you’ve added extra security to a car.

Insurers strongly favour Thatcham approved immobilisers, so if you’re adding an electronic immobiliser to an older car, always opt for a Thatcham approved Category 1 or 2 device.

Ghost immobilisers are a bit of a grey area. They’re a fairly new innovation, and many don’t align with Thatcham’s rating categories. This means most cannot yet be “Thatcham approved”. As a result, having a ghost immobiliser fitted might or might not make a difference to your car insurance premiums. This may change over time. But for now, if you’re considering having a ghost alarm fitted, it’s worth checking if there are any models that insurers are more likely to recognise.

Do I need an alarm as well as an immobiliser?

Unlike immobilisers, it is not mandatory for car manufacturers to fit alarms into new cars. Many will now install an alarm voluntarily as a selling point, but there’s no guarantee your car will have an alarm, especially if it’s an older model.

Thatcham (and therefore most insurers, too) regards a combination of an alarm and immobiliser as the top level (Category 1) of car security. So if you want to maximise your car’s security, and the potential savings you can make on your insurance, it’s a good idea to have both an alarm and an immobiliser. You can buy bundled devices or, if your car has an immobiliser but not an alarm, it’s fairly straightforward to get one added. Make sure the alarm you choose is Thatcham approved, as it’s likely to make a difference to your car insurance provider.

How else can I cut the cost of car insurance?

The security measures installed in your car are only one of many factors that affects your car insurance premiums. Here are some other tactics to keep costs down.

  • Compare insurers annually. You might find a much better deal. Even if you’re keen to stay with your current insurer, you can use comparison quotes to negotiate a better deal. Shopping around is particularly important if you’ve been through any big life changes such as getting married or moving house.
  • Avoid non-essential modifications. While added security is likely to reduce your premiums, most other modifications will do the opposite. So if you care about insurance costs, forego fancy paintwork or massive spoilers.
  • Pay annually rather than monthly if you can. Insurers apply interest if you pay in monthly instalments, so you’ll usually end up paying less if you’re able to pay in full up-front.
  • Increase your voluntary excess. Your excess is the amount you need to pay towards any claim. Typically, the higher you set the excess, the lower your insurance premium will be. Just don’t set it so high you can’t afford to pay it if you need to claim.
  • Add an experienced driver. Adding a lower-risk, experienced named driver to your policy could lower your premiums, particularly if you’re a young and inexperienced driver.
  • Drive carefully and avoid the risk of claiming. Every year that you drive safely and avoid needing to claim will increase the no-claims discount on the following year’s premiums.
  • Consider telematics insurance. This uses a small device – a “black box” – installed in your car to track your driving habits. If you drive carefully and responsibly, you should see your premiums drop.

Pros and cons of having an immobiliser


  • Modern cars almost always have one factory-fitted, so there’s no effort required to get one
  • There’s strong evidence that an immobiliser will cut the risk of your car being stolen
  • Having an immobiliser, especially a Thatcham approved one, should reduce your insurance premiums.


  • If your car was made before 1998, you may need to pay to get an immobiliser installed
  • An immobiliser isn’t a fail-safe guarantee against a smart and determined thief
  • Ghost immobilisers are so new that they’re not yet widely recognised by car insurers.

Bottom line

Immobilisers are an important car security feature. They reduce the risk of your car being stolen and, therefore, also reduce your car insurance premiums. Most people don’t need to weigh up whether or not to get an immobiliser installed in their car, as it’s been compulsory for manufacturers to include them since 1998. If you have an older car, it’s pretty straightforward to get one added. Make sure you get a Thatcham approved one, as they’re more widely recognised by insurers.

Frequently asked questions

*Based on data provided by Consumer Intelligence Ltd, (Mar ’24). 51% of car insurance customers could save £539.54
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Ceri Stanaway is a researcher, writer and editor with more than 15 years’ experience, including a long stint at independent publisher Which?. She’s helped people find the best products and services, and avoid the pitfalls, across topics ranging from broadband to insurance. Outside of work, you can often find her sampling the fares in local cafes. See full bio

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