What Is Cat S Damage? Examples and What to Check

Cat S damage is damage to the structure of a car, the load-bearing frame or chassis that holds it together and protects the people inside in a crash. It is the label given to a car that an insurer has written off, where the structure was affected but the car could still be repaired and returned to the road. GOV.UK describes Cat S as a vehicle that "can be repaired following structural damage".

That wording covers a wide range. A Cat S car might have taken a serious hit, or it might have a bent mounting point that looks like very little from the outside. This guide explains what actually counts as structural, gives realistic examples by type of impact, and shows how to tell whether a repair was done properly. For the wider picture of price, pros and cons, read our Cat S guide.

What "Structural" Means on a Car

Most modern cars are a unibody, also called a monocoque. There is no separate chassis under the body. The shell itself is the structure, built from pressed steel sections that are welded and bonded together. It is designed to stay rigid around the passenger cell and to crumple in a controlled way at the front and rear.

Insurers categorise write-offs under the ABI Code of Practice for the Categorisation of Motorised Vehicle Salvage. The code illustrates the structural areas of a typical car, and says a car has structural damage if any structural part needs realigning to its original dimensions or replacing. The areas it shows include:

• Front and rear chassis legs. The long sections at the front and rear, built to fold in a set pattern and absorb energy. The front welded crossmember is grouped with the front legs.
• The rear crossmember and the bulkhead. The beam across the back of the car, and the firewall between the engine bay and the cabin. Where the rear panel forms part of the rear crossmember, the code treats it as structural too.
• A and B pillars, side roof rails and the front and rear header rails. The uprights and rails that frame the cabin and protect it in a side impact or rollover.
• Sills. The box sections under the doors, which carry load along the car and take much of a side impact.
• Front inner wings and the upper wing supports. They look like bodywork, but the front inner wing usually includes the strut tower, which carries suspension loads and ties into the chassis leg.
• Rear inner wings and the rear wheel housings. The welded inner panels around the rear wheels.

The code says its illustrations are generic and that designs and part names differ between car makers. Other load-bearing areas, such as the floor pan, the boot floor and the points where the suspension and subframes bolt to the shell, are not each named on that list, so whether damage there counts is a judgement for the assessor.

The code is clear that parts bolted on to the shell are not structural. That covers bumper covers, front wings, the bonnet, boot lid, doors, lights, grilles, mirrors and trim. A bolted-on subframe is not structural in itself, even though the shell it bolts to is.

The edges are not always tidy. Electric cars add another grey area: on some models the battery pack forms part of the floor structure and on others it does not, so similar-looking damage can be assessed differently. That is one reason to ask what was actually damaged, not just what the category is.

Examples of Cat S Damage by Type of Impact

There is no official list of "Cat S damage". Each case is assessed individually. The table shows the kind of damage that can involve structure, by type of impact. These are illustrative examples, not rules, and they are not drawn from insurer records or statistics.

Two points are worth adding. A moderate frontal hit can leave a chassis leg folded while the bumper cover looks only scuffed. And a hard strike can distort an area near a suspension mounting point: the car may still drive, but it may not hold its alignment and the tyres can wear unevenly.

Why Modest-Looking Damage Can Still Be Cat S

Two separate decisions sit behind every Cat S car, and people often blur them.

1. Is the car a total loss? That is a financial decision made by the insurer. It weighs the cost of repair against the car's value and what the salvage would fetch. A car with expensive parts and sensors can be written off for damage that a cheaper car would be repaired for.
2. Which category does it get? That is a decision about what was damaged, made by an assessor the code calls an appropriately qualified person. The repairable categories under the ABI code are S, for structural damage, and N, for non-structural damage. They have applied since 1 October 2017, when they replaced the old C and D.

So a car does not become Cat S because the crash was dramatic. It becomes Cat S because it was written off and the assessor found a structural part that needed realigning or replacing.

That works in both directions. A car with a distorted sill can look nearly undamaged and still be Cat S. A car with a crushed bumper, two wings and a bonnet but no structural damage can be Cat N. The same impact on two different cars can also see one written off and the other repaired, because parts prices and values differ.

So do not judge a Cat S car by how the seller describes the crash. Ask what was damaged and who repaired it.

What Cat S Does Not Mean

It does not mean the crash was huge. The category says the structure was affected and the insurer paid out as a total loss. It says nothing about speed or injuries.

It does not describe the repair. The category is set when the insurer writes the car off, before any repair work. A Cat S car on a forecourt might have been repaired by an accredited bodyshop to the manufacturer's procedure, or by someone with a welder and a weekend. The record shows the category, not the quality of the work.

It does not show in the free DVLA or MOT services. Neither the DVLA vehicle enquiry nor the MOT history shows write-off status. GOV.UK says that to keep a Cat S vehicle, the owner sends the complete log book to the insurer and applies for a free duplicate using form V62, and DVLA records the category in the log book. So a V5C may show it, but do not rely on the paperwork alone.

It does not need a DVLA identity test today. The Vehicle Identity Check (VIC) scheme closed on 26 October 2015. A Cat S car takes a normal MOT when one is due, and the MOT is not a repair-quality test.

It normally stays on the record. Repair does not clear it. Expect the next buyer to ask about it.

Cat N Damage Examples by Contrast

Cat N means the car was written off but the structure was not damaged. The damage is to parts that bolt on, or to systems rather than the shell. For the full explanation, see what is a Cat N car.

Typical examples of damage that can lead to Cat N include:

• Damage to bumpers, front wings, doors, the bonnet or the boot lid
• Broken lights, grilles, mirrors and trim
• Hail damage across the outer panels
• Flood damage the insurer judges repairable. Under the salvage code, a repairable flood-damaged car is generally Cat N, while serious water damage to the cabin's electrical and safety components puts a car in Cat B
• Fire damage that did not reach the structural frame or chassis
• Damage from a theft or break-in
• Expensive sensor, camera and airbag work on a car that otherwise looks fine. Airbags firing does not on its own make a car Cat S

The contrast is simple. In a Cat N car, the damage was to bolt-on parts or systems, not to the shell. In a Cat S car, a structural part of the shell needed realigning to its original dimensions or replacing.

Cat N is not automatically safe. The salvage code itself notes that a Cat N car may still need safety-critical parts replaced, such as steering and suspension parts. A poorly repaired Cat N car can also have faulty airbags or hidden water damage. But the structural question does not arise. Our Cat N vs Cat S guide sets them side by side, and the Cat N insurance guide covers what Cat N means for cover.

What a Proper Cat S Repair Looks Like

A structural repair is skilled work with a defined process. If the seller can describe it, that is a good sign. If they cannot, that is information too.

Manufacturer repair methods

Car makers publish repair procedures for their own models. These typically specify where a damaged section may be cut, which joining method to use, and which parts should be replaced rather than straightened. Modern shells use high-strength steels that can lose strength if heated or reshaped the wrong way, so a good bodyshop works from the maker's procedure for that exact model, not from general habit. When the salvage code asks whether a car can be safely repaired, it says manufacturers' or recognised researched repair methods must always be used.

Measuring the shell

Before and after the work, the shell should be measured against the manufacturer's reference dimensions, usually with the car on a jig or bench and a measuring system. A shell that is out may not align properly and may not behave as designed in a second crash. A printout of the measurements before and after is strong evidence that this was done.

Sectioning and replacement

Heavily damaged structural sections are often replaced rather than pulled straight. Where the maker allows it, a new section is cut in at specified points. Where it does not, the whole part is replaced.

Welding and joining

Factory shells are joined by spot welds, structural adhesive and sometimes rivets. A good repair uses the joining method the maker specifies and restores the corrosion protection afterwards. The DVSA's MOT inspection manual says testers cannot accept gas brazing, soldering, adhesive bonding, fibre reinforcement or body filler for repairs to load-bearing members, and that patch repairs should generally be continuously seam welded. It does accept methods a maker recommends, such as MIG brazing or adhesive bonding combined with riveting, unless they are clearly inadequate. A repair that relies on filler, brazing or glue where the maker does not call for it is a warning sign.

Safety systems

Airbags that fired cannot be reused and need replacing, and so do seat belt pretensioners that fired. Crash sensors may also need replacing, depending on the maker's procedure. Used or counterfeit units, or a disabled warning light, are serious faults.

The paperwork

A competent repair leaves a trail. Ask for:

• The engineer's report on the original damage
• An itemised bodyshop invoice listing parts and labour
• Parts receipts, especially for airbags, pretensioners, sensors and structural panels
• Before, during and after photographs
• The jig or measurement printout
• Calibration records for cameras and radar, if the car has them
• The repairer's name and address

A seller who has this is giving you evidence. A seller who has none of it is asking you to take the repair on trust.

How to Inspect a Cat S Car You Are Thinking of Buying

Most of this is visual. None of it proves a repair is good, but it can show that one is bad, and it gives you better questions to ask. Do it in daylight, with the car dry.

Outside

• Panel gaps. Check the bonnet, doors, wings and boot lid. Gaps should be even along their length. A tapering gap, or a door that needs a slam, suggests the shell is not square.
• Paint colour and finish. View each panel from a low angle against the light and look for a change in shade or texture between neighbours.
• Paint depth. A paint thickness gauge shows where a panel has been refinished. It tells you where work was done, not whether the work was good.
• Overspray. Check rubber door seals, window rubbers, badges and trim edges for paint that should not be there.

Under the bonnet

• Inner wings and strut towers. Look for ripples, kinks, tool marks or messy seam sealer. Factory sealer is uniform and tidy.
• Chassis legs. Look along the rails for creases, repair welds and rough clamp marks from pulling the car on a frame. Neat clamp marks are normal in a repair. Poorly finished ones are not.
• Bulkhead and latch panel. Look for rewelded seams or mismatched paint. The bonnet should close without force.

Boot and underneath

• Boot floor and spare-wheel well. Lift the carpet and look for ripples, replaced sections, uneven sealant and mismatched paint.
• Sills, floor and suspension. On a ramp or with a good torch, look for crushed sections, rewelded seams, patches of fresh underseal and bent suspension arms. Poorly sealed repairs can rust early.

Inside and on the road

• Warning lights. The airbag light should come on when you switch on and go out shortly afterwards. A light that never comes on can mean the warning has been disabled. One that stays on points to a fault.
• Tracking and braking. On a quiet, flat road the car should run straight with the wheel centred and brake without pulling.
• Tyre wear. Wear on the inner or outer edges, or uneven wear side to side, points to geometry problems.
• Noises. Listen for clunks and creaks over bumps.

Driver assistance systems

Many cars have cameras behind the windscreen and radar in the bumper or grille. After a collision, or after windscreen, bumper or structural work, these may need recalibrating, and one that is out can misjudge distances or lane position. Check that every system works and ask for the calibration record.

Get an Independent Inspection

Nothing above replaces an inspection by someone who can measure the shell. Since the VIC scheme closed, there has been no official inspection of a repaired write-off before it goes back on the road or is resold, and the MOT does not do this job.

Look for an independent vehicle inspector or an engineer who works with bodyshops, rather than one recommended by the seller. They can measure the structure against the manufacturer's dimensions, check for repair methods that do not suit the car, and give you a written report. If the seller will not let you arrange one, treat that as a reason to walk away.

Factor the cost into the price you are willing to pay. If the report finds problems, you can use it to negotiate, or to withdraw.

What to Ask the Seller

• What was damaged, and was it recorded as structural?
• When was the car written off, and who repaired it?
• Can I see the engineer's report, invoices, parts receipts and photographs?
• Were the airbags and pretensioners replaced with new parts?
• Do you have the measurement printout and calibration records?
• Will you let me have it inspected independently before I pay?

If the answers differ from the record, find out why before going further. Our guide to checking a car for accident damage has more on spotting repair work, and salvage auction car history helps if the car came from an auction.

How to Check What Damage a Car Had

Insurers record write-offs on the industry's salvage and theft register, long known as MIAFTR and now run by the Motor Insurers' Bureau as Vehicle Salvage and Theft Data. The free DVLA vehicle enquiry and the free MOT history do not show it, so you need a check by registration.

A write-off check reads insurer write-off records by registration. Where the insurer recorded them, the full report shows the category, the loss date, the cause of damage and the damage locations, and it marks the recorded damage areas on a car diagram. Not every record includes a cause or locations, and a record with no damage detail is not a sign that nothing happened. The same write-off records are part of our full vehicle history report.

The free check on Carhealth covers tax, MOT, mileage and recalls. It does not include write-off data.

How to use the result:

• A category is shown. Compare it with what the seller told you. If you were told "no accidents" and the record says Cat S, you know where you stand.
• Damage locations are shown. Go and look at those areas first, under the bonnet and in the boot as well as on the outside. Ask the seller to show you what was done there.
• No damage detail is shown. The insurer's record does not include it. Rely on the paperwork and an independent inspection.
• Nothing is shown. The records held for that registration have no entry. That is useful but it is not proof of a clean history, so still inspect the car.

For a step-by-step walk through, see how to check if a car has been written off. If you are weighing up whether to buy, is it worth buying a Cat S car covers the decision itself, can you insure a Cat S car covers cover and quotes, and car write-off categories explained covers all four categories.

Frequently Asked Questions

What is Cat S damage?

Cat S damage is damage to the structural frame or chassis of a car that an insurer has written off but which can be repaired. The S stands for structural. The category is set when the car is written off. It describes what was damaged, not how well the car was repaired afterwards.

Is Cat S damage serious?

It can be. Structural parts carry and absorb crash forces, so damage to them matters more than damage to a bumper or wing. How serious it is for you depends on what was damaged and how it was repaired. A documented repair by a good bodyshop to the manufacturer's procedure is a very different prospect from an undocumented one.

What counts as structural damage?

Under the industry salvage code, a car has structural damage if any structural part of the shell needs realigning to its original dimensions or replacing. The code's illustrations show areas such as the chassis legs, crossmembers, bulkhead, pillars, sills, roof rails and inner wings. Bolt-on parts such as bumpers, front wings, bonnets and doors are not structural. In borderline cases the assessor decides.

Can Cat S damage be repaired properly?

Yes. Cat S cars are repairable by definition. A proper repair follows the manufacturer's method, measures the shell against the maker's dimensions, replaces any airbags and pretensioners that fired and leaves a paper trail. The risk is that a poor repair can look the same as a good one from the outside, so an independent inspection matters.

How can I tell what damage a Cat S car had?

Run a check by registration. Where the insurer recorded them, the full Carhealth report shows the cause of damage and damage locations and marks them on a car diagram. Not every record includes those details. Then ask the seller for the engineer's report, repair invoices and photographs, and have the car inspected by an independent expert.

Is Cat S worse than Cat N?

Cat S involves damage to the structure and Cat N does not, so Cat S carries more risk around repair quality. Both are write-offs, both normally stay on the record, and both can be repaired. See Cat N vs Cat S for the comparison.

Does Cat S show on the V5C or in the MOT history?

It may show on the V5C. GOV.UK says that when the owner keeps a Cat S vehicle, they apply for a duplicate log book using form V62 and DVLA records the category in it. Do not rely on the log book alone. The MOT history does not show write-offs at all. Use a check by registration instead.

Before You Decide

Cat S damage is not a reason to panic, and not a reason to relax. A load-bearing part of the car was damaged and an insurer chose to pay out rather than repair. What matters is what was damaged, who put it right and whether they can prove it.

Check the record by registration before you travel, ask for the paperwork and pay for an independent inspection. If the seller will not help with any of those, there will be another car.