There's a number attached to every car sold in the UK that directly affects what you'll pay to insure it. It's called the insurance group, it runs from 1 to 50, and it's set before the car even goes on sale. Most buyers never check it until they've already committed — and occasionally discover the insurance costs more per year than the monthly finance payment. That's an avoidable problem, and this guide gives you everything you need to avoid it.
Who sets the groups — and how
Insurance groups are set by Thatcham Research, an independent organisation funded by the UK motor insurance industry. Thatcham's been doing this since 1971. When a new car model's launched, Thatcham assesses it before it goes on sale and assigns it a group. That group stays with the model unless Thatcham updates it — which can happen when a new variant's introduced or when repair cost data changes significantly.
The assessment covers six main factors, and understanding them helps you predict why a car sits where it does on the scale rather than just accepting the number.
Repair cost is the most direct driver. How expensive is it to fix the car after a typical accident? Aluminium panels, complex sensor clusters embedded behind bumpers, and LED headlight assemblies that integrate cameras all push repair costs significantly. A car where a minor rear shunt triggers a £4,000 bumper-and-sensor replacement sits substantially higher than one where the same impact costs £400. This is why two cars of very similar size and performance can land in different groups — the structural and materials choices made in design affect the repair bill years later.
Parts prices feed into repair cost but are assessed separately. Thatcham prices a basket of 23 common parts for every assessed vehicle. A car where the door mirror costs £400 sits higher than one where the equivalent part costs £80. This is why premium marque cars sit in higher groups even in their base specifications — the parts are simply more expensive regardless of the car's performance. An entry-level BMW 1 Series and an equivalent Ford Focus have comparable performance, but the BMW's parts list makes it costlier to repair, and that's reflected in its group.
Repair time is assessed alongside parts cost because labour time multiplies through to the total bill. A car that takes six hours to straighten a sill after a low-speed accident sits higher than one that takes two hours. Modern cars with complex aluminium body structures and cameras or radar units integrated into every panel typically take longer — there's more to calibrate and more to replace. A sensor behind a bumper that could be tested and refitted in thirty minutes on a 2010 car might require an hour of recalibration on the same job in 2022.
Performance — specifically acceleration and top speed — affects the group because faster cars are statistically involved in more serious accidents and produce higher repair bills when they are. This is why the same hatchback in 1.0-litre base trim and 2.0-litre GTI trim can sit fifteen or more groups apart despite sharing a body and much of the structure. The engine changes the risk profile, and the group follows.
Security is assessed in terms of the fitted immobiliser, alarm, and any tracking device. Each layer reduces the group. Some manufacturers specifically offer a security-enhanced variant at a lower insurance group to make that version more competitive for cost-sensitive buyers — worth knowing if you're choosing between two trim levels and insurance cost matters. Aftermarket Thatcham-approved security devices can also reduce the effective group an insurer assigns to an older car.
Bumper compatibility is the final factor — Thatcham tests whether the bumper can absorb low-speed impacts without transferring damage to expensive components behind it. Cars that fail this test are more expensive to repair in minor accidents, including the car park bumps that represent the most common claim type in UK private motoring. A car with a well-designed bumper that stops a 5mph impact from reaching the crash sensors and cooling components behind it sits lower in group than one where the same impact reaches £1,200 of components.
The letter suffix: what E, D, U, A, and G mean
The group number is followed by a letter suffix that tells you something important about the car's security relative to Thatcham's expectation for that group. This suffix is often overlooked by buyers but it can meaningfully affect what insurers do with the number.
An E suffix (exceeded) means the car's security is better than Thatcham's requirement for that group — the immobiliser, alarm, or tracking provision is stronger than standard. An insurer may rate an E-suffixed car more favourably than the number alone implies. An A suffix (acceptable) means security meets the standard for the group, which is the outcome for the majority of assessed cars. These two suffixes represent normal outcomes and don't typically require investigation before buying.
A D suffix (provisional or descriptor) means the car hasn't received a full Thatcham assessment yet — common on very new models or significant variants released between assessment cycles. Insurers treat D-rated cars more cautiously and some won't quote until a full assessment is complete. If you're buying a very recently launched model, check whether a full assessment has been completed since the D suffix was assigned.
A U suffix (unacceptable) is the one that matters most. It means the car's security falls short of what Thatcham expected for the group it would otherwise be assigned to. Some insurers refuse to quote U-suffixed cars; others add a significant premium loading. A U suffix usually means the car lacks an immobiliser, alarm, or security standard that the group assessment assumed it would have — worth investigating specifically before buying, as retrofitting approved security may reduce the loading.
A G suffix means the car is a grey import — brought into the UK from outside the standard European market — and may have different specifications to UK-market versions of the same model. Some insurers decline to quote grey imports entirely. Others charge a meaningful loading to account for potential parts availability differences and specification uncertainty.
What the groups look like in practice
Groups 1–10 are the territory of small-engined superminis and city cars. Hyundai i10, Citroën C1 1.0, Volkswagen Polo 1.0, Skoda Fabia 1.0 MPI, Nissan Micra 1.2. These are where first-time buyers should be looking if premium cost is a constraint. A driver under 25 will generally get their most competitive quotes on cars in this band.
Groups 11–20 cover a wide band — mainstream family hatchbacks in base or mid-spec trim, small diesels, and modestly powered crossovers. A Ford Focus 1.0 EcoBoost Trend Edition, a Vauxhall Astra 1.2, or a Nissan Juke 1.0 DiG-T typically sits in this band. These are reasonable everyday cars at a premium that's manageable for most drivers over 22 or 23 with a year of no-claims.
Groups 21–35 move into larger engines, executive cars, premium marques at lower specs, and performance variants of otherwise ordinary models. A BMW 1 Series 118i (Group 22–28), an Audi A3 2.0 TDI (Group 25–30), or a Ford Focus ST-Line X 1.5 EcoBoost 182 (Group 28–32) lands here. For a young driver, the gap between a Group 8 car and a Group 25 car in annual premium terms can be £1,500 or more.
Groups 36–50 are sports cars, high-performance saloons, prestige SUVs, and anything with significant power or a repair cost that reflects premium parts. These are cars where annual insurance for a young driver can exceed the car's purchase price by a wide margin. Even experienced drivers with full no-claims pay meaningfully more.
How the same model can span many groups
One thing that trips buyers up: they check the group for "a Golf" and find Group 12, then buy a Golf GTI without realising it's Group 34. The group's assigned at variant level, not model level. Trim, engine, and body style all matter separately.
A few examples of the spread within one nameplate:
- Ford Fiesta: 1.0 EcoBoost 100ps Trend = Group 8. 1.5 EcoBoost ST-3 = Group 26. Same badge, very different insurance cost.
- MINI Hatch: Cooper 1.5 = Group 14. John Cooper Works = Group 34.
- Volkswagen Golf: 1.0 TSI Life = Group 12. GTI Clubsport = Group 38.
Always check the specific engine and trim level, not just the model name.
Electric cars and insurance groups
EVs don't automatically sit in low groups just because they lack a traditional engine. In fact, most current EVs sit in higher groups than equivalent petrol cars, because repair costs are substantially higher: battery damage assessments, sensor-dense bumper assemblies, and specialist labour all contribute. A Nissan Leaf sits in Group 18–23 depending on year. A Kia EV6 is Group 30–40 depending on variant. The Renault Zoe is one of the better-placed EVs at Group 11–15, but that's still higher than a comparable petrol city car. If you're considering an EV partly because you assume it'll be cheaper to insure, check the group first — you may be surprised.
How to check any car's group
The Thatcham Research website (thatcham.org) has a free vehicle rating database. Enter the make, model, year, and engine variant to get the group. You can also use the DVLA's vehicle enquiry service with the registration plate, which returns the group alongside tax and MOT information.
More usefully for a buyer: most major comparison sites — Compare the Market, GoCompare, MoneySupermarket — allow you to enter a specific registration and get a quote before you commit. This is a soft search and won't affect your credit file. Doing this before you view a car takes five minutes and avoids the situation where you've already paid a deposit before discovering the insurance is £800 a year more than you expected.
What you can actually control
The group itself is fixed — you cannot change it. What you can influence is what an insurer does with it when building your quote.
Adding a named experienced driver with a long clean history — a parent or partner with fifteen or more years of no-claims — can reduce the premium significantly for younger or higher-risk policyholders. The key word is honestly: the named driver must genuinely be an occasional driver of the car. Fronting — naming someone as the main driver when they never drive the vehicle — is insurance fraud, voids the policy in the event of a claim, and is detected by insurers through data matching. Done truthfully, it's a legitimate and often substantial saving.
Increasing your voluntary excess reduces the premium, but only makes financial sense if you could actually cover that excess from savings without hardship if you needed to claim. The premium saving on a £500 excess versus £250 is typically £50 to £150 per year depending on risk profile. Don't set the voluntary excess above the amount you could genuinely afford to pay tomorrow — the compulsory excess and voluntary excess are added together in the event of any claim.
Telematics and black box insurance prices the policy on actual driving behaviour rather than the group number and your demographic profile. For drivers under 25, this can halve the premium compared to a standard policy on the same car. The trade-off — lower scores for late-night driving regardless of behaviour, and potential mid-term adjustments — is manageable for most daytime commuters. See the guide on black box and telematics insurance for the full breakdown.
Declaring an accurate annual mileage rather than rounding up reduces the premium. If you drive 4,000 miles a year, don't say 8,000 to be safe — that's unnecessarily expensive. Check your actual mileage from consecutive MOT records on the DVSA's free online service. Equally, don't underestimate mileage, as a significant discrepancy between declared and actual mileage can complicate a claim.
Adding a Thatcham-approved tracker or alarm to an older car without factory security can reduce the effective group the insurer assigns. Check thatcham.org for approved devices before buying — only Thatcham-certified devices carry recognised group-reduction benefits. A Category 6 tracker (GPS and subscription-based monitoring) has the most substantial effect on the insurer's assessment of theft risk.