Defect reporting: minor, major and dangerous defects explained

When a driver finds something wrong with a vehicle, the right response depends on how serious the defect is. Since 2018, DVSA has classified all vehicle defects into three categories: minor, major, and dangerous. Understanding what each means — and what operators must do in response — is essential for any O-licence holder.

The three defect categories: where they come from

The minor, major, and dangerous defect classification system was introduced on 20 May 2018, implemented via the Motor Vehicles (Tests) (Amendment) Regulations 2017. It originated from EU Directives 2014/45/EU and 2014/47/EU on periodic roadworthiness testing and technical roadside inspections. Following Brexit, this framework is retained law in Great Britain and continues in force.

The system applies to all commercial vehicles, including HGVs and LGVs, and covers both annual tests and roadside inspections. DVSA's official reference document is the Categorisation of Vehicle Defects, most recently updated December 2024.

Note: This framework applies in Great Britain. Northern Ireland operates under a separate regime administered by the Driver & Vehicle Agency (DVA).

The official definitions

DVSA's Categorisation of Vehicle Defects document provides these definitions:

What each category means in practice

Dangerous defects

A dangerous defect means the vehicle has a deficiency that creates a direct and immediate risk on the road. Examples include brake failure, a tyre so severely damaged that a blowout is imminent, or a steering fault that compromises control.

A vehicle with a dangerous defect must not be driven. If the defect is identified during a journey, the vehicle must stop being used as soon as it is safe to do so. It cannot return to service until the defect has been assessed by a competent person and repaired.

At the roadside, DVSA can issue an immediate prohibition notice, immobilising the vehicle until the defect is rectified. This notice is attached to the vehicle and cannot be removed until DVSA has confirmed the repair.

Major defects

Major defects are serious but do not constitute an immediate road safety risk in the way dangerous defects do. At annual test, a major defect results in a fail — the vehicle cannot be issued a certificate until the defect is repaired and the vehicle re-tested or re-presented.

In an in-service context (i.e., discovered during a walkaround check rather than at formal test), DVSA guidance indicates that vehicles should not be used where it is unsafe to do so. A delayed prohibition notice can be issued, requiring repair within a specified period.

Operators should have a clear procedure for handling major defects: the vehicle should be assessed by a competent person promptly, repair work scheduled and completed without delay, and the outcome recorded.

Minor defects

Minor defects have no significant effect on vehicle or road safety. At annual test, they are recorded but do not cause a fail. In-service, they do not require immediate grounding of the vehicle.

That said, operators should not ignore minor defects. A pattern of recurring minor defects on the same vehicle is a signal that something needs attention. Proper recording and review of even minor defects is part of good maintenance practice and forms part of the evidence base that DVSA and Traffic Commissioners consider when assessing operator compliance.

Who is responsible for reporting defects?

Both the driver and the operator carry legal duties — for different things.

Drivers must carry out a walkaround check before every journey and must report any defects in writing to the person in their organisation responsible for vehicle defect management. A nil defect report — confirming the vehicle was inspected and found to be in satisfactory condition — must also be submitted when no defects are found. These nil reports are part of the maintenance record and must be kept along with defect reports.

Operators must have a robust, documented system through which drivers can report defects. The system must ensure that:

• All defects are received and assessed by a competent person
• Dangerous defects result in the vehicle being taken out of service immediately
• Repair work is carried out and completed before the vehicle returns to the road
• All steps — the report, the assessment, the repair, and the sign-off — are documented
• Records are retained for at least 15 months

What records must be kept?

DVSA guidance specifies a minimum retention period of 15 months for defect reports and related maintenance records. This aligns with the requirement to cover two annual test cycles.

Records must include:

• The defect reported (with date, vehicle, and driver details)
• Any assessment of the defect carried out
• The rectification work done and by whom
• Sign-off that the vehicle is fit to return to service
• Nil defect reports for days or journeys where no defects were found

Electronic records are acceptable, provided they contain all required information and can be produced on demand — at a roadside check, a DVSA site visit, or a Traffic Commissioner inquiry.

Consequences of failing to report or act

The consequences of systemic failure to manage defects properly are serious at both the driver and operator level:

• Roadside prohibition — DVSA can issue an immediate prohibition if a dangerous defect is found at the roadside. The vehicle cannot move until DVSA confirms the repair. A delayed prohibition requires repair within a specified period.
• “S” marked prohibition— issued where DVSA considers there has been a significant failure in maintenance compliance — for example, a defect that should have been caught at the last walkaround check or safety inspection. An S-marked prohibition triggers a follow-up investigation of the operator's maintenance systems.
• Criminal prosecution — using a vehicle in a dangerous condition is an offence under section 40A of the Road Traffic Act 1988, which carries an unlimited fine.
• Traffic Commissioner action— evidence of systemic failure can lead to a public inquiry. Traffic Commissioners have the power to suspend, curtail or revoke an operator's licence and impose personal disqualifications on operators and transport managers. Published TC decisions confirm revocations have followed serious maintenance failures.
• OCRS impact — prohibitions issued at the roadside are recorded in the Operator Compliance Risk Score, which DVSA uses to target future enforcement activity. A run of prohibition notices moves an operator from green towards red.

Practical steps for operators

• Make the defect category framework part of driver training.Drivers who understand the difference between minor, major, and dangerous defects can make better decisions in the field — but the decision to remove a vehicle from service should always involve the operator's system, not just the driver's judgement.
• Have a clear escalation path for dangerous defects. Drivers need to know immediately who to call, what to say, and what the process is. A defect that is reported but then sits in an inbox unread is still a serious compliance failure.
• Don't treat nil defect reports as optional. They are part of the maintenance record. Missing nil reports create gaps that DVSA officers and Transport Commissioners will notice.
• Review defect trends, not just individual reports.The same minor defect on the same vehicle three months in a row is not “just a minor.” It is evidence of a maintenance gap that, if unaddressed, could develop into something more serious.
• Keep records for at least 15 months, in a retrievable format. DVSA can request records going back over a year. Having them instantly available shows a well-run operation; scrambling to find them does not.

Frequently asked questions

Can a driver decide for themselves whether a defect is major or dangerous?

Drivers report what they find. The assessment of severity should involve the operator's system — specifically, a competent person who can make that judgement. Drivers should not be put in a position where they are expected to make unilateral calls about whether a vehicle is safe to operate. The operator's process should specify what to do when a defect is found, and who to contact.

Does a minor defect at annual test affect my OCRS?

Minor defects at annual test do not cause a test failure. Whether they affect OCRS depends on the specific event — a roadside inspection that identifies only minor defects may or may not generate a prohibition. Check your OCRS report for how individual events have been recorded.

Does this apply to trailers as well as powered vehicles?

Yes. The defect categories apply to trailers, and a prohibition issued against a trailer at the roadside is attributed to the operator of the towing vehicle. Trailers should be inspected as part of the walkaround check and should have their own maintenance and inspection schedule.

How long should I keep repair records?

DVSA guidance specifies a minimum of 15 months for defect reports and maintenance records. Some operators keep records longer — particularly for major or dangerous defects. Check the latest DVSA guidance and confirm requirements with your transport manager.