HGV MOT test: what testers check underneath, and how to prepare your fleet

An HGV MOT, which DVSA calls the annual test, checks 51 areas of a lorry, from lights and tyres to brakes, steering, suspension, the chassis, oil leaks and fuel tanks. Half of the ten most common failures are on parts under the vehicle. To prepare, book up to 93 days ahead, wash the underside before your pre-MOT inspection, fix what it finds, and bring the vehicle clean and laden.

Want the underside washed before your next test? Jump to when to book a pre-MOT wash.

If you're a transport or fleet manager, test day tends to go wrong in the same few ways. A defect nobody spotted because it sat under a layer of grime. A vehicle turned away because it wasn't loaded. A retest fee you didn't budget for. We wash HGVs, refuse collection vehicles and tippers at depots across the UK, and some of our regular work for councils and waste contractors is timed to MOT dates. This guide covers what the tester looks at underneath, what DVSA's own figures say fails most, and a checklist of who does what, and when.

Updated 21 October 2026. Fees and figures checked on GOV.UK the same day.

What does an HGV MOT check underneath?

Testers work from DVSA's HGV inspection manual. The version in force from 1 April 2026 lists 51 inspection areas. These are the ones that sit under the vehicle:

How much does that matter? DVSA publishes the ten most common reasons HGVs fail. For January to March 2026, in order:

1. Brake systems and components (under the vehicle)
2. Condition of tyres
3. Glass and view of the road
4. Suspension (under the vehicle)
5. Lamps
6. Oil leaks (under the vehicle)
7. Service brake performance
8. Condition of chassis (under the vehicle)
9. Steering (under the vehicle)
10. Parking brake performance

Five of the ten, including the top one, are parts under the vehicle. It's the part of a lorry that's hardest to see on a daily walkaround, and the part that collects the most road film, mud and grease.

Across the 2025 to 2026 testing year, 10.1% of HGVs failed at the first attempt. That's 45,874 out of 452,606 tests, adding up DVSA's four quarterly figures. Some defects were fixed on the spot, but 6.9% of vehicles still failed and had to come back for a retest.

Can an HGV be refused its MOT for being dirty?

Yes. Under "Acceptance for test", the inspection manual says: "The vehicle/trailer must be clean enough to allow the component parts to be inspected." The next line says it "must not present a health & safety hazard to inspect." GOV.UK's HGV MOT guide is just as plain about the cab. The inside has to be cleaned before the test, and "Your test will be cancelled and you'll have to pay again if the vehicle is not clean."

Grime causes trouble before test day too. A weeping axle seal or a chafed brake hose is easy to miss on your own pre-MOT check when it's under a coat of road film and grease. The tester, working from the pit, will find it once it's visible. Better that your mechanic finds it first.

The same section of the manual says the vehicle "must be appropriately loaded". DVSA has said it wants lorries loaded to at least 65% of their design axle weights, and won't go below 50%, because the roller brake test needs the tyres to grip. Bring a vehicle that isn't loaded and it can be refused. You lose the fee and pay again.

To be clear about what washing does: it won't fix a worn bush or a leaking seal, and it doesn't guarantee a pass. It lets someone see the problem in time to fix it.

HGV pre-MOT checklist for transport managers

This run-up to the test puts each job in the right order. Fit the timings to your own maintenance schedule.

Steps 4 and 5 are the pair to get right. A mechanic inspecting a clean underside sees what the tester will see, while there's still time to fix it.

When should you book the pre-MOT wash?

Book it before the pre-MOT inspection, not on the morning of the test. A wash just before the test helps the tester, but it leaves no time to fix anything the wash uncovers. Leave enough time for parts to arrive and repairs to be done.

On a regular wash programme it's simpler: time the deeper underside wash to each vehicle's MOT and service dates. That's how it works at Barnsley Council's depot, which also houses the council's workshop. Every RCV in the programme gets an exterior wash each week, chassis rinse included. When a vehicle is due for servicing or its MOT, our team does a detailed maintenance wash for the workshop: under-chassis cleaning, grease and mud removed, the suspension and steering cleaned, so normally hidden inspection points can be reached. The case study lists better MOT preparation and quicker workshop work among the results.

For SUEZ's municipal fleet in Somerset, MOT and service preparation washes cover the chassis rails, axles, brakes, steering, hydraulics, engine and transmission areas, and the underbody framework.

Our MOT and service preparation wash guide lists every area we clean, and our fleet washing cost guide has the guide prices. Degreasing a chassis produces oily wash water. Where your site has no suitable drainage, we capture it on wash mats and take it away for disposal, as part of our wastewater recovery work.

To book a pre-MOT underside wash, send your vehicles and test dates through our quote form or call 0800 6124 780. We reply within 2 business hours.

RCVs, tippers and trailers: what needs extra attention?

Refuse collection vehicles

On an RCV, waste, food residue, road salt and debris build up around the hopper, hydraulic rams, compaction equipment, chassis and axles. Keep the manual's health and safety line in mind here: a tester shouldn't have to work under a chassis caked in waste residue. For SUEZ, hopper dig-outs clear compacted waste by hand before a full pressure wash and sanitisation, which also gives the workshop a clean vehicle. Our RCV cleaning service covers hoppers, bin lifts and dig-outs.

Tippers

Tippers on construction and quarry work pick up mud, clay and stone dust, and it packs hard around the chassis, running gear and wheel arches. Spray suppression, wings and wheel arches have their own section in the manual (section 14), so don't stop at the chassis. Our tipper and quarry fleet cleaning covers the body, wheels, chassis and running gear.

Trailers

Trailers have their own annual test, usually due a year after the trailer was first sold or supplied. Alongside the running gear, the manual checks the coupling, the landing legs, and the parking brake, emergency brake and air line connections (sections 11 to 13). Wash the trailer's underside with the tractor unit's if they're tested close together. It's one visit instead of two.

HGV MOT test: frequently asked questions

1. How much does an HGV MOT cost?

At an authorised testing facility, the test fee is £91 for a 2-axle lorry, £113 for 3 axles and £137 for 4 or more. Trailers cost £41 to £64. The test centre can add a service charge of up to £70 for an HGV and £50 for a trailer. A lorry retest within 14 days costs £35 to £65. After 14 days you pay the full fee again.

2. How often does an HGV need an MOT?

Every year. The first test is usually due 12 months after the lorry was first registered. Trailers are usually tested a year after they were first sold or supplied.

3. How far ahead can you book an HGV MOT?

Up to 93 days ahead, for one vehicle or several. Cancel at least 3 working days before the test, or you lose the fee.

4. How long does an HGV MOT take?

GOV.UK doesn't give a standard time, so ask the test centre when you book. Arrive 10 minutes before your slot with the plating certificate and your appointment letter.

5. What are the most common reasons HGVs fail their MOT?

In DVSA's figures for January to March 2026, brake systems and components topped the list, followed by tyres, glass and view of the road, suspension and lamps. Oil leaks, the chassis and steering were also in the top ten. About 1 in 10 HGVs failed first time in 2025 to 2026.

6. Can a dirty HGV be refused its MOT?

Yes. DVSA's inspection manual says the vehicle must be clean enough for its parts to be inspected, and must not be a health and safety hazard to inspect. GOV.UK says a test is cancelled, and you pay again, if the inside of the vehicle isn't clean.

7. How laden does an HGV need to be for its MOT?

The manual says "appropriately loaded". DVSA has said that means at least 65% of the design axle weights, and no lower than 50%, so the brakes can be tested properly on the rollers.

8. Does every lorry need an HGV MOT?

Petrol, diesel and hybrid goods vehicles over 3,500 kg need one, and so do trailers over 1,020 kg unladen with powered brakes. Zero-emission goods vehicles of 3,501 to 4,250 kg take a class 7 MOT instead. Form V112/G lists the vehicles that are exempt, and some of those still need a standard MOT.

9. Does a pre-MOT wash guarantee a pass?

No. A wash doesn't fix a worn or leaking part. It lets your mechanic find faults on a clean underside before the tester does, and it means the vehicle meets the manual's cleanliness rule on the day.

10. Can you wash an HGV's underside at our depot without a wash bay?

Yes. Our team brings its own water, hot-water pressure washers, and wash mats with recovery equipment, so the oily wash water doesn't go into surface water drains. A site survey checks access and space first.