Car Insurance Groups Explained: How They Affect Your Premium

Every car sold in the UK is assigned a number between 1 and 50 by Thatcham Research on behalf of the Group Rating Panel. This number — the insurance group — is one of the factors insurers use when calculating your premium. Yet most drivers have only a vague idea of how it works. Having car insurance groups explained clearly can make a meaningful difference when you are choosing a new or used car, particularly if you are a younger driver or returning to the road after a break. This guide covers everything you need to know about the UK system.

How the 1–50 Scale Works

Group 1 is the cheapest to insure and Group 50 is the most expensive. In simple terms, a lower group means lower insurance premiums for otherwise identical drivers. The groups are reviewed annually by the Group Rating Panel, which includes representatives from the Association of British Insurers (ABI) and Lloyds Market Association. Each new vehicle model is assessed before it goes on sale, and existing models can be re-rated if significant changes are made.

It is worth noting that insurance groups are a guide rather than a fixed tariff. Insurers use them as one input alongside your age, driving history, postcode, annual mileage, and where the car is kept overnight. Two drivers with identical cars can pay very different premiums. That said, car insurance groups explained as a standalone factor: moving from a Group 20 to a Group 8 car can reduce your premium by 30–50% for a young driver.

What Determines a Car’s Insurance Group?

Thatcham Research evaluates several criteria when assigning a group rating:

• New car value — a more expensive car costs more to replace, so it sits in a higher group
• Performance — top speed and 0–60 mph time; faster cars are statistically involved in more severe accidents
• Repair costs — assessed using standard repair times and parts prices; a car with expensive or hard-to-source parts scores worse
• Parts price index — the cost of the 23 most commonly damaged parts, assessed against comparable vehicles in the same class
• Body and paint condition — cars with complex body shapes or specialist paint finishes cost more to repair cosmetically
• Security — cars with factory-fitted immobilisers, alarms, and Thatcham-approved security devices score lower (better) on this measure
• Bumper compatibility — whether front and rear bumpers align with standard crash heights to reduce low-speed repair costs

Insurance Group Suffixes: What A, D, E, P, and U Mean

You may notice that a car is listed as, say, “14E” rather than simply “14”. The letter suffix provides additional information about the vehicle’s security status:

• A — Acceptable; the car meets security requirements for its group
• D — Doesn’t meet requirements; the car has been placed in a higher group than its other attributes would suggest, due to poor security
• E — Exceeds requirements; the car has better-than-required security and has been placed in a lower group as a result
• P — Provisional rating pending full assessment, typically for new models
• U — Unacceptable; the security is so poor that a group cannot be assigned — very rare
• G — Grey import; the car was not originally designed for the UK market

How Insurance Groups Interact with MOT Status

While insurance groups are assigned at manufacture, the ongoing condition of your car can indirectly affect your insurance costs. A car that repeatedly fails its MOT with safety-related defects may flag concerns about maintenance standards, and some specialist insurers ask about MOT status at renewal. More practically, driving without a valid MOT invalidates most standard insurance policies — meaning you could be driving uninsured without realising it.

You can confirm your vehicle’s current MOT status and expiry date with a free MOT check. If you are researching a used car purchase, viewing the full MOT history will show you whether the vehicle has a pattern of recurring failures that could indicate maintenance neglect.

Practical Tips for Choosing a Low-Group Car

With car insurance groups explained, you can make smarter purchasing decisions. Here are some practical guidelines:

• For young or newly qualified drivers, target Groups 1–10. Cars in this range include small-engined city cars such as the Fiat Panda, Volkswagen Polo 1.0, and Vauxhall Corsa 1.2.
• Check the insurance group of specific trims before committing to a purchase — a sportier trim of the same model can be two or three groups higher than the base version.
• Factory security upgrades (Thatcham-approved alarms and tracking devices) can lower your group rating. Aftermarket additions do not change the official group but may earn a discount from some insurers.
• Use the free Thatcham vehicle data lookup or run a free car check by registration to confirm the exact specification of any used car you are considering.

Do Insurance Groups Change Over Time?

Yes, though it is relatively uncommon for established models. New assessments are triggered when a manufacturer makes significant mechanical or structural changes to an existing model, introduces a new trim level with different performance specifications, or when Thatcham revises its methodology. Entirely new models are always assessed before going on sale. For buyers of used cars, the insurance group is effectively fixed at the level assigned to that specific variant when it was built — a 2019 car does not get re-rated unless the model undergoes a significant mid-cycle refresh.

Understanding car insurance groups explained in this way makes it clear that the group is a property of the vehicle, not the owner. It travels with the car throughout its life, which is one more reason to research any used car thoroughly before buying.