MOT advisory explained
“Seat belt anchorage prescribed area is corroded”
Rust in the metal that a seat belt is bolted to, nearly always the sill. Of every advisory about the body of a car, this is the one most likely to be a failure at the next test, and it is the one where the repair is welding rather than paint. It deserves the front of the queue.
Each seat belt bolts to a reinforced point in the body, and the MOT treats the metal within thirty centimetres of that bolt as a prescribed area, held to a stricter standard than the rest of the shell. The tester found rust inside that zone and judged it not yet excessive.
12.6% fail on a seat belt anchorage at the next test, one in eight. That is the highest conversion of any body corrosion advisory, and it rises with age. Only 21.0% are advised again, because rust this close to a mounting does not get left alone twice.
Underseal, sealant or filler over rust in a prescribed area is not a repair. Testers probe through it, and a covered-over anchorage that fails at the next test has to be cut back further than an honest one. Get it welded, and get a receipt that says so.
A “seat belt anchorage prescribed area is corroded but not considered excessive” advisory means rust has been found in the body metal within thirty centimetres of a seat belt mounting, usually in the sill, but not yet severe, so the car passes. The repair is welding. According to DVSA MOT data analysed by PriceMyRepair, 12.6% of 194,901 such advisories followed to the next test failed on a seat belt anchorage, the highest of any body corrosion advisory.
Why a seat belt mounting is special
The load it carries. In a collision the belt holds a body weighing seventy or eighty kilograms against a deceleration of many times gravity. The bolt at the base of the belt sees several tonnes of pull for a fraction of a second. It is bolted to a reinforced plate in the sill or floor, and everything within thirty centimetres of that plate is what stops it tearing out.
Where the rust is. “sill” is the most common note by far, then “outer sill” and “inner sill”. The lower belt mounting for each front seat sits at the base of the sill, and the rear belts bolt to the floor or the inner wheel arch. “floor”, “wheel arch” and “inner wheel arch” cover the rest.
How it is judged. The tester probes the area with a tool. Rust that has not reduced the thickness of the metal is this advisory. Rust that has thinned it, or that the probe goes through, is excessive and a failure, whether or not the anchorage itself is affected.
Will it fail next year?
One wording, recorded 636,194 times, with 194,901 followed to the same vehicle’s next MOT.
| What happened at the next test | Share |
|---|---|
| Failed on the same component | 12.6% |
| Same advisory recorded again | 21.0% |
According to DVSA MOT data analysed by PriceMyRepair: 194,901 advisories followed to the same vehicle’s next test. Rows can overlap.
Compare the other corrosion advisories. General structural rust fails 4.9% of the time, rust within thirty centimetres of a mounting generally 4.7%, rust at a suspension mounting 10.2%. The seat belt anchorage is above all of them.
Part of that is the standard: the seat belt area is judged more strictly than almost anything else on the underside. Part is location. A sill that has rusted enough to be noted near a belt mounting has usually been rusting from the inside for years, and the next winter finishes it.
| Advisory wording | Fails on same part | Advised again | Followed |
|---|---|---|---|
| Seat belt anchorage prescribed area is corroded | 12.6% | 21.0% | 194,901 |
| Suspension component mounting prescribed area is corroded | 10.2% | 24.2% | 1,521,106 |
| Brake pipe corroded, covered in grease or other material | 10.1% | 44.4% | 7,889,073 |
| Vehicle structure is corroded but structural rigidity is not significantly reduced | 4.9% | 25.5% | 1,233,347 |
| Integral body structure or chassis corroded within 30cm of a mounting, | 4.7% | 15.2% | 289,591 |
| Seat belt webbing slightly damaged or frayed | 3.1% | 23.6% | 1,047,800 |
| Sub-frame corroded | 2.0% | 39.8% | 2,445,675 |
Under seven years there is nothing to report. From 7–9 years the rate climbs from 0.1 per 1,000 tests to 7.3 at 20 years and over, and the share that fail next time climbs with it, from 7.8% to 13.6%.
| Age of car | Per 1,000 tests | Fails on same part | Followed |
|---|---|---|---|
| 7–9 years | 0.1 | 7.8% | 5,258 |
| 10–12 years | 0.9 | 11.2% | 26,844 |
| 13–15 years | 2.6 | 12.7% | 55,238 |
| 16–19 years | 4.9 | 13.2% | 64,319 |
| 20 years and over | 7.3 | 13.6% | 38,680 |
The rusted metal is cut out back to sound steel, a new section is welded in with continuous seam welds, and the repair is sealed and painted. On a sill that usually means a repair panel or a fabricated section along the lower edge, made to reach the anchorage plate.
Ask for the welding to be photographed before it is sealed, and keep the photos with the invoice. The next tester, and the next buyer, will both want to see them.
A repair that only patches the visible outer sill, leaving a rotten inner sill behind it, will fail at the following test on the inner. Ask the welder to check both.
Exact wording on your certificate
One advisory and one failure, separated by the word excessive.
| Line on the certificate | Result | Code |
|---|---|---|
| Seat belt anchorage prescribed area is corroded but not considered excessive | Advisory — pass | 7.1.1 (a) (i) |
| Seat belt anchorage prescribed area is excessively corroded | Major — fail | 7.1.1 (a) (ii) |
The rear corners lead, with the offside rear and nearside rear ahead, and the fronts and unsided entries spread behind. The rear belt anchorages sit in the wettest part of the floor, above the rear wheels, and the rear of the sill is where the mud packs.
| Position written by the tester | Share of all instances |
|---|---|
| Offside rear | 12% |
| Nearside rear | 11% |
| Offside | 11% |
| Nearside | 9% |
| Offside front | 9% |
| No position recorded | 9% |
From 636,194 recorded instances. Testers can add their own note after the standard wording. The most common on this advisory: “sill” (115,875), “outer sill” (60,445), “inner sill” (25,313), “floor” (14,250), “wheel arch” (7,547), “inner wheel arch” (5,476), “sill area” (5,009), “sills” (4,335).
What it costs
Welding is quoted per section, and a seat belt anchorage repair can range from a short patch on a floor to replacing most of a sill. The spread is too wide for an honest range, so we do not publish one. Ask for a written quote that names the anchorage and includes cutting back to sound metal. Other prices are on the repair costs index.
Can I still drive with this advisory?
The question is what it would do in a crash, and the honest answer is that it has less margin than the car was built with. Book the welding for this season rather than the next MOT. If the rust is at a rear anchorage and you carry children in the back, do it sooner.
Enter your reg to see every corrosion advisory on your car’s record, and whether the sills were noted in earlier years before the belt mounting was.
Which cars get this advisory most?
The all-vehicle rate is 1.3 per 1,000 tests. On the models below it is between two and ten times that.
| Model | Per 1,000 tests | Vs all cars | Tests |
|---|---|---|---|
| Mazda MX-5 | 14 | 10.2× | 962,840 |
| Mitsubishi Shogun | 10 | 7.7× | 420,039 |
| Ford Ka | 7 | 5.6× | 2,120,213 |
| Fiat Punto | 6 | 4.2× | 1,031,944 |
| Land Rover Discovery | 5 | 4.1× | 1,610,504 |
| Ford Transit | 5 | 3.9× | 9,907,752 |
| Toyota Hilux | 4 | 2.6× | 734,628 |
| Mazda 6 | 3 | 2.6× | 728,629 |
| Ford Puma | 3 | 2.5× | 306,285 |
| Volkswagen Beetle | 3 | 2.5× | 586,588 |
Model families are grouped by the first word of the DVSA model name, so “Transit” covers every Transit variant. Only models with at least 60,000 tests are ranked.
The Mazda MX-5 is in a class of its own at 10.2 times the average. Its sills are a known weak point, it is kept for decades, and the front belt anchorages sit exactly where the sill rusts first. The Ford Ka, Fiat Punto and Ford Puma are small cars with the same reputation for sills.
The Mitsubishi Shogun, Land Rover Discovery, Ford Transit and Toyota Hilux are the working vehicles that appear on every corrosion list. Bare steel, salt, and long lives.
What to do next
- Identify the belt. Front or rear, which side. The certificate normally says. The rear ones are used least and rust most.
- Get two welding quotes. Ask each to state how far they will cut back and whether the inner sill is included.
- Have it done before the salt. Rust that is an advisory in September is often a failure by spring.
- Keep the evidence. Photos of the welds and the invoice. They are worth money when you sell and time at the next test.
Seat belt anchorage corrosion FAQ
What does seat belt anchorage prescribed area is corroded mean?
Rust has been found in the body metal within thirty centimetres of a seat belt mounting, usually in the sill or floor. The tester judged it not yet excessive, so it is an advisory and the car passes.
Will it fail the MOT next year?
More often than any other body corrosion advisory. According to DVSA MOT data analysed by PriceMyRepair, 12.6% of 194,901 such advisories failed on a seat belt anchorage at the next test, and only 21.0% were advised again.
How is a corroded seat belt anchorage repaired?
By cutting the rusted metal back to sound steel and welding a new section in, usually a sill repair panel or a fabricated piece reaching the anchorage plate. Filler or sealant over the rust is not an acceptable repair and will not pass.
How much does it cost?
It is a welding job quoted per section, from a small floor patch to most of a sill, so we do not publish a range. Get written quotes that name the anchorage. Any prices on this site are estimates and final quotes come from garages.
Is it safe to drive?
In normal driving, yes. The concern is a collision, when the belt pulls on that mounting with several tonnes of force. The advisory means the surrounding metal has less margin than it should. Have it repaired this season, not at the next test.
Which cars get this advisory most?
The Mazda MX-5, at 10.2 times the average rate, with the Mitsubishi Shogun, Ford Ka and Fiat Punto behind it. Small cars with weak sills and body-on-frame 4x4s dominate the list.
How these figures were calculated. According to DVSA MOT data analysed by PriceMyRepair, from the DVSA anonymised MOT test results (Open Government Licence v3.0): 350,943,111 tests. This advisory was recorded 636,194 times; 194,901 of those were followed to the same vehicle’s next test between 180 and 730 days later. “Fails on the same part” means a failure at that next test under the same defect code and naming the same component, on either side of the vehicle. Testers do not always name a component the same way twice, so the figure is a floor. Method and how to cite.