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Road Users

Modified vehicles

Vehicle conversions or modifications.

If you make a change to the manufacturer's original design of a vehicle, such as changing the engine or suspension system, it is considered a modification. There is no law against modifying a vehicle, but any modifications you make must be carried out to an appropriate safety standard.

Remember, it's the law and it's your responsibility as a vehicle owner and driver to ensure that your vehicle is maintained in a safe and roadworthy condition at all times.

This content is for general information only. It does not, and is not intended to, provide legal or technical advice or to represent a legal interpretation of the matters it addresses.

Frequently Asked Questions (FAQs)

Modifying or converting a vehicle

Definitions of modifications and conversions, suitably qualified individuals (SQI), CVRT modification reports.

A newly manufactured vehicle must meet strict safety standards before it can be placed on the market. Modifying that vehicle can affect its original strength or operation and therefore safety. We do not recommend modifying vehicles, however in some cases adaptations are unavoidable e.g., for disabled use or access. It is important to remember that under Irish road traffic regulations, it is the responsibility of the owner and/or driver to ensure that their vehicle is maintained in a roadworthy condition at all times when used in a public place. Therefore, any modification which negatively affects that roadworthiness can result in prosecution.

A vehicle conversion refers to a distinct type of post registration physical modification that results in a change of the vehicle’s category e.g., passenger car to van. A conversion can also result from other changes to a vehicle that will also affect the registration details of a vehicle e.g., a change in the number of seating positions. Vehicle conversions require a declaration of conversion to be provided to the Revenue Commissioners.

A Suitably Qualified Individual (SQI) is a certified professional who by definition meets a minimum standard of competency to carry out a robust technical assessment of a vehicle modification or conversion. To meet the minimum standard of competency an SQI must have:

  • An engineering or technical qualification (Level 7 or higher accredited course), or appropriate accreditation with Engineers Ireland or the Institute of Automotive Engineer Assessors.
  • A minimum of five years’ experience working in a suitable technical environment (preferably an automotive or engineering environment) and
  • Appropriate professional indemnity insurance

Engineers Ireland have a search function available on their website where you can check whether the SQI is an Associate Engineer or Chartered Engineer. Also if needed, you can check whether their engineering qualification is accredited. The Institute of Automotive Engineers Assessors (IAEA) has a “Find an Engineer” search option available on their website. The IAEA also has a list of registered members on their website.

For M1 unregistered vehicles being adapted or modified to be used as a Wheelchair Accessible Vehicle (WAV) in Ireland requires type-approval.

More information on how to adapt a vehicle for disabled use can be found on the NSAI website.

In order to re-classify a vehicle or amend its vehicle registration certificate, you will need to contact Revenue to see if there are any VRT implications.  If there are no VRT implications, you will need to contact your local motor tax office.

Since May 2018, once a vehicle has been converted, for example, from an M1 passenger vehicle to an N1 goods vehicle, it is required to be tested immediately in line with the date of conversion and in its new test category.

For further information on the commercial vehicle roadworthiness test (CVRT), please visit the CVRT website

Down-rating or up-rating a vehicle

Definition of down-rating and up-rating a vehicle.

Down-rating, down-weighting, or down-plating a vehicle is when an owner wants to lower a vehicle’s original design gross vehicle weight (DGVW) or maximum authorised mass (MAM). This is the weight of a vehicle or trailer including the maximum load it can carry as designed by the manufacturer.

Contact original vehicle manufacturer before any proposed changes to the vehicle design weights.

Up-rating, up-weighting, or up-plating a vehicle is when an owner wants to increase a vehicle’s original DGVW. Doing this will also increase the load carrying capacity of the vehicle. In most cases a physical modification is required because carrying a heavier load requires stronger brakes, better suspension etc. Up-rating a vehicle may result in additional legal obligations such as a higher licence category, a tachograph, a speed limiter etc. which can be viewed under embedded links. Further information on the Guidelines for Maximum Weights and Dimensions for Vehicles and Trailers. Up-rating a vehicle must not be carried out without manufacturer’s approval.

Converting a vehicle from a private (M1) to a commercial (N1)

Definitions of M1 and N1 vehicles, reclassification of converted vehicles.

The process and procedures required to reclassify a vehicle from a passenger to commercial are available on the Revenue website. See their declaration of conversion form

It is a passenger or private vehicle designed and constructed to carry passengers and comprising of no more than eight seating positions in addition to the drivers seating position e.g., people carriers, SUVs etc.

This is a light goods or commercial vehicle designed and constructed to carry goods with a maximum mass not exceeding 3,500 kg e.g., delivery vans, light trucks etc.

The process and procedures required to reclassify a vehicle from passenger to commercial post registration are available on Revenue's website. See also Declaration of conversion form.

No. An N1 vehicle is classed as a commercial or goods vehicle and therefore must be tested every year at a CVRT centre. Also note that if your vehicle has been physically modified in any way, e.g. seats removed to enable the conversion from M1 to N1, you will need to present a Modifications Report at its next roadworthiness test.

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