Corrosion within a load-bearing or safety-critical area has weakened the structure. Prescribed areas include the regions around suspension mountings, seat belt anchorages, steering components and the load-bearing structure itself.
Wording as it commonly appears on an MOT certificate: “Excessive corrosion in a prescribed area”.
What does it mean?
Corrosion within a load-bearing or safety-critical area has weakened the structure. Prescribed areas include the regions around suspension mountings, seat belt anchorages, steering components and the load-bearing structure itself.
How serious is it?
Usually recorded as: Major, Dangerous. The tester assesses the actual vehicle on the day, so your certificate is what counts.
What normally causes it?
- Road salt over many winters
- Stone damage breaking through the underbody coating, then rust working underneath it
- Blocked drain holes in sills and doors holding water
- Previous accident repair where sealant was applied over bare metal
What a mechanic would check
On the ramp with a light and a small hammer, cleaning back the flaking areas to see whether it's scale on the surface or whether the metal has gone. I'll take photos so you can see it yourself and make an informed decision, because this is the failure that most often decides whether an older car is worth keeping.
What might need replacing
- Cut-and-weld repair with new plate, seam sealed and protected
- In severe cases, an honest scrap-or-repair conversation
Can you still drive it?
Depending on where it is and how bad, this ranges from Major to Dangerous. Structural corrosion affects how the car behaves in a crash, so it isn't something to run on while you think about it.
Repair cost
Welding is priced by hours and access, and the bill can quickly exceed the value of an older car. Get it looked at in person and get an honest opinion before spending anything.
Before the retest
Corrosion and structural repairs need to be done properly — welded steel, not filler or underseal painted over rust. Ask for photos of the repair before it is sealed so you know what was done. Run your hand carefully along the edges of bumpers, trims and arches before the retest and make sure nothing sharp or loose remains that could catch a pedestrian.
Retest rules
If the vehicle stays at the test centre for repair and is retested within 10 working days, a partial retest is often free; some items qualify for a free retest if you bring the car back by the end of the next working day. The exact conditions are set out on GOV.UK, so confirm with the test centre before you leave. A major or dangerous failure means the car cannot legally be driven away unless the previous MOT is still valid and nothing dangerous was recorded — check your certificate first.
Related help
More body and structure failures · MOT failure decoder · Ask a mechanic about your certificate
This is general guidance from a UK mechanic, not a substitute for a physical inspection. Only the tester who inspected your vehicle can confirm what was recorded and why.