Car Write-Off Categories Explained: Cat A, B, S & N (2026)

By James Fletcher, Carhealth motoring editor — last updated 11 July 2026

Every year, over 500,000 vehicles are written off by insurers in the United Kingdom. Many of them quietly re-enter the used car market, listed on Auto Trader and Facebook Marketplace with nothing in the advert to alert you. Some have been expertly repaired and represent genuine value. Others are dangerous. The difference between the two often comes down to which write-off category the car received — and whether the seller is being upfront about it.

This guide explains every current UK write-off category in plain language: what each one means, what physically happened to the car, whether it can legally return to the road, and what the implications are for your wallet, your insurance, and your safety.

If you already own or are considering a specific vehicle, you can run a free history check by registration plate to see whether it carries a write-off marker before you read any further.

Quick Reference: The Four UK Write-Off Categories at a Glance

The table below gives you the essentials. Everything that follows expands on each row in detail.

The single most important distinction buyers ask about is the difference between Cat S and Cat N. Both can legally return to the road, but Cat S involves structural damage to the vehicle's core — the parts responsible for protecting you in a crash — whereas Cat N does not. That distinction is explained in full further down.

Key Takeaways

• The UK operates four write-off categories: Cat A, Cat B, Cat S, and Cat N.
• Cat A and Cat B vehicles cannot legally return to public roads. The body shell must be crushed.
• Cat S and Cat N can be repaired and returned to the road, but must carry a permanent write-off marker on their history.
• The 2017 rule change replaced the old Cat C and Cat D classifications with Cat S and Cat N to better describe the nature of damage.
• Insurers typically write off a car when repair costs reach 50–70% of the vehicle's pre-accident market value.
• A write-off marker never expires. It appears on vehicle history checks indefinitely, regardless of how good the subsequent repair was.
• Before buying any used car, check its full history to see whether it has ever been written off.

The History: From Cat A, B, C and D to the Current System

Before October 2017, the UK used a four-category system labelled A, B, C, and D. Most people in the motor trade still use the old letters interchangeably with the new ones, which causes confusion.

The old Category C meant the car was repairable, but repair costs exceeded the vehicle's market value. The old Category D meant the car was repairable and repair costs were below market value — though the insurer still chose not to proceed, often for reasons of logistics, parts availability, or complexity.

The problem with C and D was that neither label told you anything about the type of damage. A Category D car might have a bent chassis that had been badly straightened, while a Category C car might have superficial panel damage that simply made it uneconomic to repair through a main dealer at main dealer rates.

In October 2017, the Association of British Insurers (ABI) and the British Vehicle Salvage Association (BVSA) introduced the current system in partnership with the DVLA. The new labels — S for Structural and N for Non-structural — describe what was damaged, not just the economics of the repair. This was a genuine improvement for buyers.

The old Cat A and Cat B categories were carried over unchanged. If you encounter a car with a "Cat C" or "Cat D" marker on a history report, it means the write-off occurred before October 2017, and you should interpret it roughly as Cat S (for Cat C) or Cat N (for Cat D) — though not with exact equivalence, because the criteria were assessed differently.

How Insurers Decide to Write Off a Car

When a driver makes an insurance claim after an accident, the insurer appoints an independent vehicle assessor — sometimes called an engineer or loss adjuster — to examine the damage and produce a repair estimate. The insurer then weighs that estimate against several factors.

The Repair-to-Value Ratio

The most significant factor is the repair-to-value (RTV) ratio: the cost of repair expressed as a percentage of the vehicle's pre-accident market value (also called the CAP or Glass's clean retail value). Most mainstream UK insurers will write a car off when the repair estimate reaches somewhere between 50% and 70% of market value, though the exact threshold varies by insurer.

A car worth £8,000 before the accident might be written off if repairs are quoted at £4,500 — even though it could technically be fixed. The insurer's calculation also accounts for:

• Salvage value: What the damaged car can be sold for at auction to a salvage dealer. If the insurer can recover £2,000 from salvage, the effective write-off threshold rises, because writing it off becomes more economical sooner.
• Storage and courtesy car costs: A complex structural repair taking six to eight weeks generates significant additional costs beyond the bodywork itself.
• Parts availability: For older, rarer, or popular models with supply chain issues, parts prices can push repair estimates far above the actual structural damage would suggest.
• Labour rates: An independent bodyshop charges far less than a franchised main dealer approved repairer. Insurers use benchmarked labour rates, and the difference between approved and non-approved rates can be substantial.

Rising Write-Off Numbers

It is worth noting that write-off volumes have increased significantly in recent years. The combination of higher new-car prices (which inflated the used-car values that RTV ratios are calculated against) and sharply rising parts and labour costs since 2022 means that cars are being written off at lower levels of physical damage than they were five years ago. A minor front-end shunt that would once have been repaired can now tip the economics toward a write-off.

Category A: Scrap Only — No Exceptions

Category A is the most severe classification. It is applied to vehicles so badly damaged that they cannot be repaired under any circumstances — and crucially, they cannot have any parts removed for re-use in other vehicles.

A Cat A write-off must be delivered to an Authorised Treatment Facility (ATF) and crushed in its entirety. The ATF issues a Certificate of Destruction, and the DVLA must be notified so the vehicle's record is closed. The V5C (logbook) is surrendered and cancelled.

Why Cat A Exists

The category exists to prevent the most dangerous vehicle components — safety cages, crumple zones, airbag systems, and structural metalwork — from being removed from wrecked cars and fitted to other vehicles. If a chassis is severely twisted, the metal has been work-hardened and weakened in ways that are not visible to the naked eye. Allowing that metalwork to be recycled into another car would be dangerous.

Can You Buy a Cat A Car?

No — and nor should you want to. There is no such thing as a Cat A car being legally available for sale as a vehicle. If someone offers to sell you a car and it later emerges the vehicle has a Cat A marker on its history, the transaction is likely fraudulent, and the car itself is illegal to drive. Always run a history check before any purchase.

Category B: Body Shell Crushed, Parts May Be Salvaged

Category B sits one step below Cat A in severity. The vehicle's body shell — the structural frame, sills, pillars, and floor — is beyond repair and must be crushed. However, Cat B allows salvageable components to be removed before crushing. This is where salvage yards and specialist breakers make much of their business.

Mechanical components such as the engine, gearbox, drivetrain, suspension parts, wheels, and interior trim can be removed, tested, and sold as used parts. Electrical systems, infotainment units, seats, and other non-structural components may also be salvaged. The V5C is surrendered, and a Certificate of Destruction is issued for the body.

The Practical Difference From Cat A

The distinction matters in one specific way: if you buy a used component from a breaker, that part might have come from a Cat B car. There is nothing wrong with this for mechanical or interior parts — the component itself is not structurally compromised. What you cannot do is buy a Cat B car's body shell or structural members to repair another vehicle.

Can You Buy a Cat B Car?

Again, no. If a V5C has been surrendered and a Certificate of Destruction issued, the vehicle no longer legally exists as a vehicle. It cannot be registered, taxed, MOT'd, insured, or driven. Be extremely cautious of any listing that mentions a Cat B car being available for purchase — it is either being misrepresented or is fraudulent.

Category S: Structural Damage — Repairable but Serious

Category S is the first of the two categories where a vehicle can legally return to UK roads. The "S" stands for Structural — meaning the damage has affected the vehicle's core structural components. These are the parts that determine how well the car protects its occupants in a collision.

What Counts as Structural Damage?

When an insurer classifies a car as Cat S, the damage will typically have affected one or more of the following:

• The chassis or monocoque body shell — the welded steel structure that all other components bolt to
• Crumple zones — the front and rear sections designed to absorb and dissipate crash energy
• The A, B, C, or D pillars — the vertical columns that support the roof and door apertures
• Sill sections — the longitudinal members running beneath the door openings, which form part of the side-impact protection
• Suspension mounting points — towers, subframes, and crossmembers that locate the suspension geometry
• The floor pan — particularly the transmission tunnel and areas around seat mounting points

Damage to any of these areas compromises the vehicle's ability to perform as designed in a subsequent accident. A crumple zone that has already crumpled cannot crumple again in the same controlled way. A straightened sill may look fine but will have lost some of its resistance to side-impact intrusion.

What Happens After a Cat S Classification?

When an insurer writes a car off as Cat S, they notify the DVLA, which records the marker permanently on the vehicle's history. If the registered keeper or the salvage buyer then wishes to repair the vehicle and return it to the road, the following must happen:

1. Professional structural repair — the work must be carried out by a competent bodyshop with the appropriate equipment, including a chassis jig capable of measuring alignment to within two millimetres.
2. Post-repair inspection — while not a legal requirement, a post-repair inspection from an independent assessor (such as those offered by the Institute of Automotive Engineer Assessors) gives buyers evidence of repair quality.
3. Valid MOT — the vehicle must pass an MOT before being driven on public roads. The MOT tester is not specifically briefed on the Cat S status, but structural problems will show up during the inspection.
4. Insurance — the owner must declare the Cat S status when obtaining insurance cover.

The Cat S marker cannot be removed from the vehicle's history. No amount of repair work, time, or change of ownership erases it.

For a dedicated guide to buying Cat S vehicles, including what to look for and which inspections to commission, see our Category S write-off guide.

Category N: Non-Structural — Easier to Repair, Still Worth Knowing About

Category N covers damage that does not affect the vehicle's structural integrity. The "N" stands for Non-structural. The car's chassis, frame, pillars, and crumple zones are undamaged; the write-off decision was made on economic grounds rather than structural ones.

What Counts as Non-Structural Damage?

Cat N damage typically falls into one or more of these categories:

• Cosmetic panel damage — bumpers, bonnets, wings, doors, boot lids that are dented, torn, or scraped
• Electrical damage — wiring harnesses, ECUs, sensor arrays, and infotainment systems that are expensive to diagnose and repair
• Airbag deployment — replacing an airbag system, including the module, sensors, wiring, and all deployed bags, can cost £3,000–£8,000 on a mid-range car, making a write-off economically straightforward
• Mechanical damage without structural involvement — a damaged engine, gearbox, or suspension component that is expensive to replace but does not affect the body shell
• Flood or fire damage where the structure is intact — though these are complex cases and require thorough inspection

The critical point is that a Cat N car, once properly repaired, should perform structurally as it did before the accident. The safety cage is intact.

Returning a Cat N Car to the Road

Cat N is simpler to return to the road than Cat S. There is no requirement to notify the DVLA before driving it again, though the insurer will have already updated the DVLA's records with the write-off marker. After appropriate repairs, the car needs a valid MOT and insurance (declared as a Cat N vehicle), and it is road-legal.

For our complete analysis of Cat N cars — including how much discount to demand and which models are worth considering — read our what does Cat N mean guide.

The Difference Between Cat S and Cat N

This is the question most buyers have, and it is worth answering precisely:

Cat S means the vehicle's structure was damaged. Cat N means it was not.

Structurally, a properly repaired Cat N car should be essentially indistinguishable from an undamaged equivalent. A properly repaired Cat S car should be safe, but there is an inherent and unavoidable uncertainty: you are relying on the quality of structural metalwork repair that is hidden under paint and underseal.

In practical terms, here is what that means when buying:

• Cat N can often be bought with confidence if you can verify the repair was completed (MOT history, service stamps, receipts from a reputable bodyshop) and you are getting an appropriate discount of at least 15–20%.
• Cat S demands more due diligence — an independent post-repair structural inspection costing £150–£300, full documentation of the repairs, and a discount of at least 25–30% to compensate for the permanent stigma and resale difficulty.
• Both carry a permanent write-off marker that will be visible to any future buyer who runs a history check.

If a seller cannot explain clearly which category the car holds, or claims the marker has been "cleared" or "removed," walk away.

Returning a Write-Off to the Road: The Full Process

Category S: Steps to Roadworthiness

1. Acquire the vehicle from the insurer or salvage auction (Cat S cars are commonly sold through specialist salvage auctions like Copart, IAA, or BCA Salvage).
2. Commission structural repairs from a bodyshop with a chassis jig and experience of structural work. Ask for itemised invoices and before/after photographs.
3. Request a post-repair inspection from an independent assessor to certify the structural repair.
4. Book an MOT at a DVSA-approved testing station. The MOT will check alignment, suspension, brakes, lights, and general roadworthiness.
5. Obtain insurance — declare the Cat S status when getting quotes. Specialist brokers such as Adrian Flux, Flux Direct, or A-Plan can often provide cover when mainstream comparison sites cannot.
6. Update your V5C if ownership has changed. Contact the DVLA to ensure the registration is transferred correctly.

Category N: Steps to Roadworthiness

1. Complete the necessary repairs — cosmetic, electrical, or mechanical, as appropriate.
2. Ensure a valid MOT is in place (or obtain one if the existing certificate has expired during the repair process).
3. Obtain insurance with the Cat N status declared.
4. No DVLA notification or special inspection is required from the registered keeper.

Insurance Implications of Buying a Write-Off

You Must Declare the Write-Off Status

When applying for car insurance, you are required to disclose any material facts that would affect the insurer's decision to provide cover or the premium they charge. A write-off classification is a material fact. Failure to declare it is misrepresentation and will void your policy — meaning any claim you make could be refused.

What Happens to Premiums?

Cat N: Most mainstream insurers will cover Cat N vehicles. Expect to pay a premium uplift of roughly 10–25% compared to the equivalent clean vehicle. The uplift reflects the administrative complexity of valuing a Cat N car in the event of a subsequent claim, rather than an assessment of ongoing risk.

Cat S: Fewer mainstream insurers will cover Cat S vehicles. Those that do typically charge 20–50% more than for a clean equivalent. You are more likely to need a specialist broker, and the pool of insurers willing to quote will be smaller, which itself limits competitive pricing. Some mainstream comparison-site insurers will simply return no quotes for a declared Cat S vehicle.

Cat A/B: There is nothing to insure — these vehicles cannot be on the road.

Agreed Value Policies

If you are buying a Cat S or Cat N car that has been professionally restored, it is worth exploring an agreed value policy rather than a market value policy. Market value policies will account for the write-off status in any settlement, potentially leaving you short. An agreed value policy settles at a figure both you and the insurer agree upfront.

Finance Implications

The majority of mainstream motor finance providers — banks, captive finance arms of manufacturers, and the largest independent lenders — will not advance money against a Cat S or Cat N vehicle. This is primarily a risk management decision: write-offs are harder to value accurately, harder to sell in the event of repossession, and carry greater residual value uncertainty.

In practical terms, this means:

• PCP (Personal Contract Purchase) and HP (Hire Purchase) are almost never available for Cat S cars, and frequently unavailable for Cat N cars through mainstream dealers.
• Unsecured personal loans can be used to buy a write-off, as the lender holds no security interest in the vehicle itself.
• Specialist finance brokers occasionally offer secured lending on Cat N vehicles at higher rates.
• Cash purchase is the most common route for write-off buyers, which naturally limits the buyer pool and depresses residual values further.

If you are budgeting to buy a Cat S or Cat N car on finance, be clear-eyed: the options are limited and the rates on available products will be uncompetitive.

Resale Value: The Permanent Price Penalty

The write-off marker never leaves a vehicle's history. Every buyer who runs a vehicle history check will see it — and the market prices accordingly.

Typical Value Reductions

Cat S: A Car that would be worth £10,000 in clean condition will typically trade at £6,000–£8,000 as a Cat S, depending on the quality of the structural repair, the availability of documentation, and the specific model. High-demand models in short supply lose proportionally less; models with a ready supply of clean examples lose more.

Cat N: A car worth £10,000 clean will typically trade at £7,500–£8,500 as a Cat N. The discount is smaller because buyers are more comfortable with non-structural damage, and some Cat N repairs (particularly cosmetic panel damage) are genuinely invisible after a quality repair.

The Compounding Problem

The write-off penalty compounds across the life of the vehicle. If you buy a Cat S car today and keep it for five years, the eventual buyer will still pay a write-off discount at that point. The discount does not erode over time the way, say, depreciation does. This means the total cost of ownership over a holding period where you eventually want to sell is higher than a simple purchase-price comparison suggests.

How to Check If a Car Has a Write-Off Marker

The most reliable way to check whether a specific car is recorded as a write-off in any category is to run a full vehicle history check using the registration plate.

What a History Check Reveals

A comprehensive vehicle provenance check cross-references the registration plate and VIN against:

• DVLA records — including V5C history, keeper changes, and SORN status
• Insurer databases — including the ABI's Claims and Underwriting Exchange (CUE), which records write-offs notified by insurers
• Police databases — for recorded stolen vehicles
• Finance databases — for outstanding finance agreements (HP, PCP, leasing)
• Mileage records — from MOT tests, servicing, and previous checks

Carhealth's car history check covers all of these. You can also view a sample report to understand what the output looks like before purchasing, or see how it compares to other providers.

Free Government Checks: What They Do and Do Not Show

You can check a vehicle's MOT history for free at the DVSA's official tool on gov.uk. This shows pass and fail records, mileage at test, and advisory notes. It does not show write-off status.

You can check the DVLA's vehicle enquiry service for basic registration details — make, model, colour, tax status, and whether an MOT is recorded. Again, it does not show write-off status.

A free Carhealth free check will show the key markers — including write-off status — so you can identify red flags before deciding whether to pay for a full report.

Should You Buy a Write-Off Car?

There is no universal answer — it depends on which category, what the repair history shows, and how much of a discount you are receiving.

When It Can Make Sense

• Cat N with documented repair and a 20%+ discount: If the damage was cosmetic and the repair was done to a professional standard, a Cat N car can represent good value for a buyer who is comfortable keeping it long-term and does not need to sell quickly.
• Cat S with full structural documentation, independent inspection, and a 30%+ discount: This is a higher-risk proposition, but experienced buyers with access to specialist inspection services can find genuine value in Cat S cars.
• Budget buyers who cannot stretch to a clean example of the same model: Sometimes a well-repaired write-off is a safer choice than a cheap unwritten-off car of unknown maintenance history. A Cat N car with a documented repair and service history can be more transparent than a clean-paper car with hidden wear.

When to Avoid

• If you plan to sell within three to five years — the write-off discount you buy at will not fully recover.
• If you need finance — the product options are too limited.
• If repair documentation is absent or incomplete — you have no way to assess quality.
• Cat S without an independent structural inspection — the risk is too high without it.
• Any car where the seller is not disclosing the category upfront — if you discovered the status via a history check rather than the seller's disclosure, that is a serious red flag.

Frequently Asked Questions

What is the difference between Cat S and Cat N?

Cat S (Structural) means the vehicle sustained damage to its structural components — the chassis, frame, crumple zones, pillars, or sill sections — in the accident that led to the write-off. Cat N (Non-structural) means the vehicle was written off for economic reasons, but the structure itself was not damaged. Both can legally return to the road after repair, but Cat S requires structural repair work and carries a greater safety caveat if that work was not done properly.

What are the write-off categories A, B, S and N?

The four current UK insurance write-off categories are: Category A (catastrophic damage — vehicle must be crushed entirely, no parts may be salvaged); Category B (severe damage — body shell must be crushed, but mechanical and interior parts may be removed and sold); Category S (structural damage — vehicle can be repaired and returned to road, but structural components were damaged); and Category N (non-structural damage — vehicle can be repaired and returned to road; structure was not affected).

Do you need to re-register a Cat S car with the DVLA?

You do not need to re-register a Cat S vehicle with the DVLA, but the write-off classification must be declared when transferring ownership and when applying for insurance. The DVLA will already have been notified by the insurer and the marker will be permanently attached to the vehicle's record. If the V5C has been surrendered to the insurer, a new V5C must be obtained before taxing and driving the vehicle.

Can you insure a written-off car?

Category A and B vehicles cannot be insured because they cannot legally be on the road. Category S and N vehicles can be insured, but you must declare the write-off status when applying for cover. Cat N cars are covered by most mainstream insurers, though at a premium uplift. Cat S cars can be harder to insure through comparison sites, and you may need a specialist broker. Failing to declare write-off status when applying for insurance is misrepresentation and will void your policy.

What happens when a car is declared a write-off?

When an insurer decides not to repair a damaged vehicle, it is classified into one of the four write-off categories based on the severity and nature of the damage. The insurer notifies the DVLA, which records the category permanently on the vehicle's history. If it is a Cat A or B, a Certificate of Destruction is issued and the V5C is cancelled. If it is a Cat S or N, the vehicle can pass to the registered keeper or be sold to a salvage buyer, repaired, and returned to the road — though the write-off marker remains on its record indefinitely.

How do insurers decide to write off a car?

An independent vehicle assessor evaluates the damage and produces a repair estimate. The insurer compares this figure against the vehicle's pre-accident market value. When the repair cost reaches roughly 50–70% of market value (the exact threshold varies by insurer), writing the car off typically becomes more economical than repairing it. The insurer also factors in the salvage value it can recover by selling the damaged vehicle, the cost of a courtesy car during lengthy repairs, and parts and labour availability. Vehicles that are totalled on structural grounds may be written off even when repair costs are below this threshold, if the structural damage makes a safe repair commercially unviable.

Final Thoughts

Understanding write-off categories is one of the most practical things you can do as a used car buyer. The four labels — Cat A, Cat B, Cat S, and Cat N — are not bureaucratic box-ticking; they represent meaningful distinctions about what happened to a specific vehicle, whether it is safe to drive, and what it is worth.

The essential takeaway is this: always check before you buy. A write-off marker is one of the first things any vehicle history report will flag, and finding out after you have handed over cash is an expensive way to learn. Whether you run a free check to screen for red flags or go straight to a full vehicle history report, spending a few minutes and a few pounds before committing protects you against one of the most common pitfalls in the used car market.

For deeper reading on the two repairable categories, see our dedicated guides:

• Category S write-offs: should you buy one?
• What does Cat N mean and is it safe to buy?