What Is a Thatcham Device? Every Category Explained, and What Your Insurer Means
A Thatcham device is a vehicle security product, such as an alarm, an immobiliser, locking wheel nuts or a tracker, that Thatcham Research has tested against the British insurance industry's criteria for vehicle security and placed in a numbered category. When an insurer asks about one, it either wants to know what security your car left the factory with, or it is asking you to fit a particular tracker category. For a Thatcham S5 requirement, the Meta Trak S5 Tracker is from £295 and the ScorpionTrack S5 costs £375, both for supply and installation, and the system we recommend is the Meta Trak S5 DEADLOCK from £469, which puts an immobiliser alongside the tracking.
This guide explains where the categories come from, what each one covers, what the old Category 5, 6 and 7 tracker numbers mean today, how to find out whether your car already has a Thatcham device, and which product answers which insurer request.
Who Thatcham are, and why your insurer cares
Thatcham Research was set up by the motor insurance industry in 1969, and in written evidence to Parliament in 2016 it described itself as the UK's only not for profit, insurer funded research centre. Its security categories date back to the 1990s and now sit under the name Thatcham Security Certification. A certified product has been tested for security, reliability and safety, and Thatcham reviews each certification every two years.
That shared yardstick is why the word turns up on insurance forms. It gives an underwriter one consistent way to describe how hard a car is to steal or break into, without having to know every manufacturer's system. It is not a blanket guarantee of acceptance, though. Thatcham's own certification page says that certification does not guarantee insurer recognition, because that is agreed separately between each product manufacturer and its insurance partners. The wording on your policy is always what counts.
The Thatcham categories, one by one
Thatcham's certification page currently lists six categories. In plain terms:
Category 1
Electronic alarm and immobiliser
An alarm and an immobiliser certified together as one system. A car that left the factory with both may have its system listed under this category.
Category 2
Electronic immobiliser
An immobiliser with no alarm. It sets itself without the driver doing anything and isolates at least two separate circuits. New cars sold in the UK have had to carry a factory fitted immobiliser since October 1998, and that unit is rated Thatcham Category 2.
Category 2-1
Electronic alarm
An alarm added to a vehicle that already has a Category 2 immobiliser. You may see it written as 2/1 or 2.1.
Category 4
Wheel locking devices
Locking wheel nuts. They protect the wheels themselves rather than the car.
Category S5
Vehicle tracking systems
A monitored tracker with driver recognition. The driver carries an ID tag, so the system can tell an unauthorised journey from an authorised one and alert the monitoring centre while the theft is under way.
Category S7
Asset location systems
A monitored tracker without driver recognition. It helps locate the vehicle once the owner knows it has gone.
Two other labels still appear in guides and on quote forms. Category 3 covered mechanical immobilisers such as steering wheel and gear lever locks, and it is no longer one of Thatcham's current categories. Q class is the term used for aftermarket security products that sit outside the Thatcham categories altogether. A Q class product is not automatically a weak one, a point we come back to below.
The difference between S5 and S7 matters most when an insurer has named one of them. Our Thatcham S5 tracker buyer's guide sets out how driver recognition works and what each category asks of a tracker.
Category 5, 6 and 7: the old tracker numbers
If your paperwork mentions a Cat 5 tracker, it is using a name that Thatcham retired in January 2019, when the numbered tracker categories gave way to S5 and S7. S5 is the new name for the previous Category 5, and S7 was introduced at the same time to supersede the old Categories 6 and 7.
In practice, a policy schedule, a renewal letter or a forum post asking for a Category 5 tracker is describing what is now a Thatcham S5 tracker. If yours names Category 6 or Category 7, ask the insurer which of today's categories they want before you buy anything. A two line email now is quicker than fitting the wrong system and starting again.
How to tell whether your car already has a Thatcham device
Comparison site forms often ask you to choose between options along the lines of a factory fitted Thatcham approved alarm, a factory fitted alarm that is not Thatcham approved, or none, and owners regularly turn to car forums to ask which one applies to them. These are the checks that settle it:
- Read the security section of the handbook. Manufacturers usually say whether the car has an alarm, an immobiliser or both. If you bought the car used and have no handbook, ask the seller or a dealer for the make.
- Check Thatcham's National Listing. Thatcham publishes a Vehicle Security National Listing of the manufacturer systems it has assessed, set out by make, system, model and fitment years, with separate Category 1 and Category 2 sections. Issue 122 was published in September 2026. The listing applies to dealer specification vehicles only, so a car imported privately from abroad may not match its entry.
- Look for paperwork on anything fitted later. An aftermarket alarm or tracker should have come with a certificate of installation, and Thatcham's website lets you look up certified aftermarket products.
- Ask before you guess. If none of that settles it, ask the insurer how they want your car's security recorded. The answers you give on a quote form are part of the information your cover is based on, so it is worth getting this one right.
For most cars built since 1998 the answer comes down to one question: did the car leave the factory with an alarm as well as the immobiliser? If it did, the system may be listed as Category 1. If it has the immobiliser alone, it will usually be Category 2. The National Listing shows how your model was assessed.
What a Thatcham rating does not tell you
The immobiliser on almost every car on UK roads is a certified Category 2 unit, and it is also the part today's thieves get past. It is wired into the car's own network and acts on what the car's electronics tell it, so once a relay attack, a cloned key or CAN injection has convinced those electronics that a genuine key is present, the factory immobiliser stands down as designed. Our car immobiliser buyer's guide goes through that weakness step by step.
A pouch for your key or a fob that sleeps when left still can stop a relay attack, but neither does anything against CAN injection, which leaves the key out of it entirely. What changes the outcome is an immobiliser fitted after the car was built, outside the factory network, that waits for its own authorisation before it allows the car to start.
That is also why a missing Thatcham label does not mean a product is ineffective. The Meta AUTOBLOK is not a Thatcham certified product, and that says nothing about how well it works. The Meta AUTOBLOK operates independently of the vehicle's factory electronics, so it blocks the start attempt whichever method was used, including relay attacks, key cloning, OBD port attacks and CAN injection.
So treat the category as a record of what a product has been tested and certified to do, which is exactly what an insurer needs to see. When you are choosing protection for its own sake, judge it on how and where it immobilises the car.
When your insurer names a category
- A Thatcham S5 tracker. Any of our Thatcham S5 trackers meets it. Insurers ask for S5 mainly because of what the car is worth, backed up by theft numbers, and on high value cars it is often a condition of cover.
- A Thatcham S7 tracker. Any of our Thatcham S7 trackers meets it. A Thatcham S5 tracker is also accepted, because S5 is the higher accreditation: you are simply installing more than your insurer requires.
- A tracker, with no category given. Ask which category they mean. The answer decides whether an S7 tracker will do.
- An immobiliser. Check whether the wording names a Thatcham category. Send us the exact wording first and we will confirm which of our systems meets it.
- Confirmation of existing security only. Nothing needs fitting. Use the checks above and answer the question accurately.
Each tracker below is Thatcham certified in its category and accepted by UK insurers that require that category of tracker.
A tracker finds the car. It does not keep it
A tracker does not prevent a theft. It gives the monitoring centre and the police the means to find the car afterwards, which is what an insurer wants because a recovered car costs it far less than an unrecovered one. QuestGates' analysis of DVLA figures, published in February 2026, counted 53,629 private cars stolen in the UK in 2025 and put the share recovered at 44.94 percent, so more than half were not recovered.
That is why our advice is a combined tracker and immobiliser whatever the insurer has strictly asked for: the immobiliser stops the car being driven away, and the tracker is there if it is taken anyway. One more thing to know before you choose. Without an active subscription a tracking system cannot communicate and stops working, whichever brand it is, and on a combined system the immobiliser stops too. You can compare every tracker and immobiliser system we fit.
What we recommend for each request
Our recommendation
Thatcham S5 tracking and an immobiliser in one system
Supply and installation
From £469
Subscription
First term chosen at checkout, plus £189.95 for 1 year or £499.95 for 3 years. Renewals then go directly to Meta Trak.
Warranty
Lifetime Meta Trak parts and labour warranty (original owner, active subscription)
Insurer asks for S5
From £295, plus a first term chosen at checkout: £189.95 for 1 year or £499.95 for 3 years. Renewals are paid directly to Meta Trak. Lifetime Meta Trak parts and labour warranty (original owner, active subscription).
£375 for supply and installation only; the subscription is arranged and paid directly with ScorpionTrack once it is fitted. 2 year manufacturer warranty.
Insurer asks for S7
From £185, plus a first term chosen at checkout: £119.95 for 1 year or £329.95 for 3 years, with later renewals paid to Meta Trak directly. Lifetime Meta Trak parts and labour warranty (original owner, active subscription).
£185 for supply and installation only, with the subscription set up and paid with ScorpionTrack itself after fitting. 2 year manufacturer warranty.
Immobiliser on its own
For protection rather than an insurer's category
Supply and installation
£349
Subscription
None
Warranty
3 years
Why the DEADLOCK is our pick. It meets a Thatcham S5 requirement on its own, and every DEADLOCK variant has an aftermarket immobiliser that takes no instructions from the factory CAN bus, so the start attempt is refused whatever the car's electronics have been told. It immobilises automatically: without an authorised driver ID tag present the engine will not start, so there is nothing to remember to switch on. The system includes a Thatcham CAT2E accredited immobiliser, covered in our Category 2E guide.
Choosing between the two S5 trackers. If your insurer only asks for a Thatcham S5 tracker, the Meta Trak S5 Tracker and the ScorpionTrack S5 both satisfy it, each has its own strengths, and the choice is yours. Our ScorpionTrack S5 buyer's guide covers that system in detail.
Electric and hybrid cars. If your car has any electrified powertrain (MHEV, PHEV or full EV) and its make is on Meta Trak's E-TEC compatibility list, the Meta Trak S5 DEADLOCK E-TEC, from £599, is most likely compatible and is the system we recommend. A car that will go into drive showing Ready on the dash, without anyone pressing the start button, takes the standard DEADLOCK instead, and the standard DEADLOCK can be fitted to any make, model and powertrain. If you are unsure which applies, call 0330 133 3990.
Getting the proof your insurer asks for
Order online and, for a Meta Trak tracking system, pick your first subscription term at checkout. We arrange the fitting at home or at work anywhere in the UK, with supply and installation in an estimated 2 to 5 days, and the system is tested once fitted to confirm it is fully functioning. After activation, the product manufacturer emails you the certificate of installation that insurers ask for, and some manufacturers also show it in their app. Forward it to your insurer and keep a copy with your policy documents.
Not sure which Thatcham device your insurer is asking for?
Answer a few quick questions and get a tailored recommendation for your vehicle, from a compliant S5 Tracker to a full tracker and immobiliser setup with OBD protection. It takes about two minutes.
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Frequently asked questions
What is a Thatcham device?
A Thatcham device is a vehicle security product that Thatcham Research has tested and certified in one of its security categories, which cover alarms, immobilisers, wheel locks and trackers. Thatcham was set up by the motor insurance industry, and insurers use its categories as a common way to describe how well a vehicle is protected. Your policy wording decides which category, if any, you need.
What are the Thatcham categories?
Thatcham's certification page lists six: Category 1 (electronic alarm and immobiliser), Category 2 (electronic immobiliser), Category 2-1 (electronic alarm), Category 4 (wheel locking devices), Category S5 (vehicle tracking systems, with driver recognition) and Category S7 (asset location systems). Category 3, for mechanical locks, still appears in some guides, and Q class describes aftermarket products that sit outside the categories.
Is a Category 5 tracker the same as a Thatcham S5 tracker?
Yes, in practice. Thatcham replaced its numbered tracker categories with S5 and S7 in January 2019, and S5 is the current name for what was Category 5. S7 superseded the old Categories 6 and 7. If your insurer still refers to Category 6 or 7, ask which current category they want before you order.
How do I know if my car has a Thatcham approved alarm or immobiliser?
Start with the security section of the handbook, or ask the supplying dealer. Thatcham's Vehicle Security National Listing shows the manufacturer systems it has assessed, by make, model and fitment years, under Category 1 or Category 2, for dealer specification vehicles. Cars sold new in the UK from October 1998 onwards all have a factory fitted immobiliser, so the usual question is whether the car also left the factory with an alarm.
Is an immobiliser without a Thatcham category worth fitting?
It can be, if what you want is protection rather than a category for your insurer. The Meta AUTOBLOK is not Thatcham certified. The Meta AUTOBLOK operates independently of the vehicle's factory electronics, so it blocks the start attempt whichever method was used, including relay attacks, key cloning, OBD port attacks and CAN injection. It costs £349 for supply and installation, with no subscription. If your insurer requires a certified product, choose one that is certified.
Which Thatcham device do you recommend?
For most cars, the Meta Trak S5 DEADLOCK, from £469 for supply and installation. It meets a Thatcham S5 tracker requirement and adds an immobiliser that does not take instructions from the factory CAN bus, so you get prevention as well as recovery. Where only a tracker is needed, an S5 requirement is met by either the Meta Trak S5 Tracker from £295 or the ScorpionTrack S5 at £375, and for an S7 requirement there is the Meta Trak S7 from £185 or the ScorpionTrack S7 at £185.
Get the right Thatcham device fitted
Send us your policy wording, get a tailored recommendation, or browse every system we fit.
Sources
- Association of British Insurers and Thatcham Research, written evidence to a UK Parliament committee inquiry (AUV0051), 26 October 2016.
- Thatcham Research, Thatcham Security Certification, web page read 12 October 2026.
- Thatcham Research, Vehicle Security National Listing, Issue 122, September 2026.
- QuestGates, analysis of DVLA data on the UK's most stolen car makes and models in 2025, 11 February 2026.
Pricing accurate at time of publishing.
