NMO Technical Services

Product certification, quality management system certification, pre-assessment, and standards calibration.

Changes to Conformity Assessment Body Services

Changes in the broader test house and conformity assessment landscape have made it necessary for the Office for Product Safety and Standards (OPSS) to consider the way it operates its statutory and commercial metrology services, in particular its role as a Conformity Assessment Body (CAB) for metrology products.

OPSS will be ending its provision of commercial Conformity Assessment Body (CAB) services under the NMO brand. This will be a managed exit, ensuring alternative provisions for businesses are in place before stepping back from the market.

OPSS will continue to uphold its statutory metrology services and its place as an expert leader in legal metrology. Ceasing our CAB commercial services will enable us to focus more on our key areas, increasing our support for local government and UK businesses, both nationally and internationally.

Product certification, quality management system certification, pre-assessment, and standards calibration

Manufacturers can draw on our specialised conformity assessment services to enable them to place regulated weighing and measuring instruments on the market. These include items as diverse as beer glasses, fuel dispensers, precision balances, railway weighbridges, supermarket scales, taximeters and water meters.

The Measuring Instruments Regulations 2016 (as amended) and the Non-automatic Weighing Instruments (NAWI) Regulations 2016 (as amended) supply the legal framework for conformity assessment within the UK.

Outside the UK, recommendations for specific weighing and measuring instruments are produced by the International Organisation for Legal Metrology (OIML).

Our client services

NMO Technical Services offers two main types of conformity assessment:

  • Product certification, sometimes called type examination, involves the rigorous assessment of instruments at the design stage to ensure they comply with the regulations
  • Quality management system certification is the approval of your processes for producing an instrument, or verifying it following its repair or modification

We also provide:

  • Pre-assessment, for those unsure whether their product or quality management system will satisfy certification requirements
  • Standards calibration for businesses and local authorities

Temporary closure of calibration laboratories during ongoing refurbishment

Due to the ongoing refurbishment programme in Teddington to upgrade all building facilities and services, the calibration laboratories will be shut down from 1 October 2021 until April 2022. During this time our statutory work will continue, however there will be an impact on our turnaround times. Local Authorities should email for further details on statutory work and estimated lead times. Non-statutory work customers should use the UKAS website to search by category for alternate calibration suppliers. NMO will be contacting customers whose goods have already been received to make suitable arrangements.

Standard terms and conditions for sale of goods and services (PDF, 101 KB, 4 pages)

Support is available for organisations that are required have competent legal metrology staff by law.

OPSS works with the Chartered Institute of Trading Standards to provide free legal metrology training for all local authorities.

Legal metrology training courses for local authorities

For further information please contact:

Legal Metrology Training
Office for Product Safety and Standards
Stanton Avenue
TW11 0JZ

Our accreditations

Our accreditations are external endorsements of our work. NMO – part of the Office for Product Safety and Standards within the Department for Business, Energy and Industrial Strategy – is:

UKAS accreditation

NMO’s calibration, testing, product certification and Quality Management System certification services are accredited by the UK Accreditation Service (UKAS). The scope of NMO’s accredited services is specified in schedules of accreditation that can be found by searching for ‘NMO’ on the UKAS website.

  • Calibration – UKAS reference number 0205
  • Testing – UKAS reference number 0004
  • Quality management system certification – UKAS reference number 0135
  • Product certification – UKAS reference number 0135

We are also responsible for national type approval and verification of certain instruments under the Weights and Measures Act 1985.

Our facilities

The equipment in the laboratories at our Teddington site is fully traceable to national standards, operated in accordance with ISO/IEC 17025:2017, and available for research or pre-assessment testing.

NMO testing facilities

We liaise closely with the legal metrology team in OPSS, whose guidance on the Weights and Measures Act 1985 and related matters will be relevant to many of our existing and potential customers. This extends to training and consultancy.

National regulation: Weights and Measures

Certificates issued by NMO


We are currently in the process of updating our Guide to certification services.

It includes technical annexes on:

  • automatic weighing instruments
  • non-automatic weighing instruments
  • liquids other than water
  • cubic measures
  • intoxicating liquor measuring equipment and capacity serving / transfer measure equipment
  • material measure of length
  • water meter certification
  • taximeters
  • thermal energy meters
  • gas meter and volume conversion devices certification
  • active electrical energy meters certification
  • dimensional measuring instruments

Information on OIML approvals

Weights and measures technical updates

Contact for further information

Head of NMO:

Impartiality committee

The impartiality committee ensures that policies, practices and operations are in accordance with ISO 17021-1:2015-1, ISO 17025: 2017 and ISO 17065:2012 and all guidance relating to these standards issued by the International Accreditation Forum and NMO’s accreditation body.

The committee comprises a minimum of 3 people. The chair and at least 2 other people are not NMO personnel. NMO is represented by the Quality Manager, or his or her deputy. The membership is selected to ensure no single interest predominates.

The role of the committee is to:

  • assist in developing the policies relating to the impartiality of NMO activities
  • counteract any tendency to allow commercial or other considerations to prevent the consistent objective provision of NMO activities

The committee advises on matters affecting confidence in NMO activities including openness and public perception, and conducts a review, at least once annually, of the impartiality of NMO activities.


Should you wish to make a complaint about the services we provide, write to:

Head of Quality:


  • explain your complaint and any related issues
  • provide examples or supporting evidence where possible
  • describe the action you would like us to take to resolve matters

Process overview

  1. Acknowledgement – All complaints will be acknowledged within 2 working days, but we aim to acknowledge them immediately.
  2. Investigation – The Quality Manager will ensure a full investigation is carried out, the level of which will be commensurate with the frequency of occurrence and severity of the complaint.
  3. Response – Once the investigation has concluded, we will address the complaint by taking the necessary action.
  4. Communication – The decision in relation to the complaint will be documented, recorded, and sent to the complainant within 10 working days from the acknowledgment of the complaint.


Should you wish to appeal against a technical or certification decision we have made, write to:

Head of Quality:

Appeals may be made, for example, against our decisions to refuse or suspend certification for an instrument or management system, or in relation to the grading or validity of non-conformities.

Your appeal will be acknowledged within 2 working days. If deemed valid, it will be reviewed and a decision communicated to you within 10 working days from the acknowledgment of your appeal. A robust explanation for our decision will be included.

Health and safety

OPSS recognises that the work of NMO contains hazards relating to its laboratory-based activities and for that reason is committed to achieving certification of its approach to managing those hazards through the British Standard for Occupational Health and Safety BS ISO 45001:2018.

NMO health and safety policy and objectives (PDF, 28.8 KB, 1 page)

Published 2 April 2014
Last updated 7 September 2021 + show all updates
  1. OPSS will be ending its provision of commercial Conformity Assessment Body (CAB) services under the NMO brand. This will be a managed exit, ensuring alternative provisions for businesses are in place before stepping back from the market.

  2. Updated to reflect changes to the regulations at the end of the transition period.

  3. Page content revised, now including links to dedicated pages on product certification, quality management system certification, pre-assessment, and standards calibration.

  4. The Guide to Certification Services has been updated to version 3.

  5. Video added introducing NMO Certification and Technical Services.

  6. The document "A guide to NMRO Certification Services" has been updated to revision 2 and is now called "A guide to NMO Certification Services" dated (27 July 2017).

  7. Addition of a guidance publication relating to the activities of the NMRO Certification Services, and link to weights and measures technical updates.

  8. Addition of information regarding the complaints and appeals processes

  9. Amended to include information on management system certification marks and restrictions of use.

  10. This Guide has been updated to include a link to Legal metrology training: support of national competency for UK trading standards officers, and international consultancy services

  11. First published.