Weighing equipment for legal use

This guidance is for England, Scotland and Wales

Weights and measures (also known as 'legal metrology') legislation enforced by Trading Standards services places requirements on weighing equipment for use when goods are bought, sold or produced. It covers weighing equipment that determines the final quantity of goods delivered to customers.

The legislation also applies to equipment used for weighing patients for the purpose of medical monitoring, diagnosis and treatment, as well as weighing equipment used for making up medicines on prescription in pharmacies and determination of mass in analyses carried out in medical and pharmaceutical laboratories.

There are also other particular weighing applications where this legislation applies, which include the calculation of tolls, tariffs, taxes, bonuses, penalties, etc based on weight; and expert opinions given in court proceedings concerning weights and the application of laws.

Weighing equipment used during a production process (for example, to determine the weight of ingredients) does not need to comply with this legislation, neither do check scales for consumers' use in supermarkets etc, provided there is a further final weight check over an authorised, accurate and correctly marked weighing machine.

Equipment types, uses and construction

The controls over weighing equipment depend on its type of construction and the use to which it is put. All weighing equipment that this legislation applies to must be suitable for its intended purpose in terms of its construction, weighing capacity and level of accuracy; it must indicate weight correctly to within defined limits.

Weighing equipment can be either:

• 'non-automatic' where goods are placed on the equipment by the user and the weight indication is displayed and can be printed if required
  or
• 'automatic' as used in production lines (for example, where goods pass over the equipment to ensure the quantity is correct without intervention by an operator)

Weighing machines for legal use have to be constructed to a particular Government specification and bear particular conformity markings, stamps, stickers or other indications to show that the equipment complies with these requirements. The required indications have changed over the years and examples of them are outlined later in this guide.

Additionally, weights that are used in conjunction with weighing equipment must be correctly constructed and bear particular indications to show that they are suitable for legal use.

When considering using any weighing equipment for legal use, it is recommended that the assistance of your local Trading Standards service be sought. They will be able to advise on the suitability of equipment, which is particularly important in relation to second-hand equipment.

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Construction, type approval and verification

Weighing equipment used for legal purposes must be accurate and manufactured in accordance with an approved type approval or examination certificate.

Weighing instruments are either:

• passed as 'fit for use for trade' by an inspector of weights and measures or an approved verifier
  or (and more commonly these days)
• 'qualified' for legal use by an approved manufacturer, a notified body, an inspector of weights and measures or, following adjustment or repair, an approved verifier

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Stamps, stickers and other markings

When weighing equipment for legal use has been made and qualified as conforming to all manufacturing and accuracy requirements the required stamps, stickers and other indications are attached to it by the manufacturer or approved qualifier. Some equipment - weighbridges, for example - is required to be tested and have its final approval stamps applied when the equipment has been installed in its place of use.

As can be seen, the appearance of these markings has changed as legislation has developed and been subjected to amendments over the years, with more changes being introduced as new requirements are introduced. When considering the purchase of new or used weighing equipment the stickers and stamps may not be exactly as illustrated below due to these ongoing changes. Local Trading Standards services will, however, be able to advise on the current stamp and sticker requirements for particular equipment.

The following examples of stamps and stickers may be found on weighing equipment that has been approved for legal use.

The crown stamp, qualifier's identification stickers, etc

The crown stamp, year of application and official number of the inspector of weights and measures who passed the equipment as fit for trade use is found on a lead plug embedded into older, traditional weighing equipment.

The M sticker indicates that the equipment it is attached to has been manufactured in accordance with legal metrology requirements. The year of manufacture appears next to the M.

The approved body / notified body sticker indicates which organisation examined and approved the equipment as being in accordance with all manufacturing and accuracy requirements.

The requalification sticker indicates that the equipment has been repaired or adjusted since it was manufactured, to maintain manufacturing and accuracy requirements. The examples below are those used by, respectively, inspectors, approved verifiers and approved manufacturers.

    

UKCA, CE and UKNI marking

For the GB market only, products assessed against UK rules by a UK approved body will be UKCA marked followed by the M symbol and year of manufacture.

The UKCA mark is Great Britain's replacement for the CE mark. Guidance on the UKCA mark can be found on the GOV.UK website.

For the UK market (GB and Northern Ireland), products assessed against EU rules by an EU notified body will be CE marked followed by the M symbol and year of manufacture.

The CE mark indicates that the equipment has been manufactured in accordance with all relevant EU legislation (incl. low voltage electromagnetic compatibility, restriction on hazardous substances, etc).

Equipment placed on the market in Northern Ireland using a UK approved body requires the UKNI marking. These instruments are also valid for the GB market. See the GOV.UK guidance on the UKNI mark.

Data plate

Approved weighing equipment is also required to bear various other indications relating to the weighing capacity, accuracy, etc, as detailed on the approval certification, with more modern equipment having the required information on an attached 'data plate' or tamper-proof label. The data plate or tamper-proof label (as illustrated below) may also have the required stickers attached so that all required information is contained on the instrument in one easily discernible position.

Newer equipment may also have the manufacturer's or importer's name, address and trade mark displayed on the data plate, as well as additional information relating to different tare intervals, safe loads, operational temperatures, etc.

The data plate also commonly includes information relating to electrical rating, power consumption, etc.

Typical data plates

Typical data plate pre-2017

Newer equipment may also have some of the required markings indicated on the equipment's display screen rather than permanently displayed on the equipment body.

The accuracy of approved weighing equipment is divided into four classes, and careful consideration must be given to which accuracy class should be used for particular weight determination.

Classes of weighing equipment

Class	(I)	(II)	(III)	(IIII)
Accuracy	Special	High	Medium	Ordinary
Use	Precious metals, precious stones, pharmaceutical purposes, etc		General weighing purposes	Ballast and other building materials, waste disposal and recycling purposes

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Weighing equipment that has been rejected for legal use

When considering the purchase and use of second-hand weighing equipment for trade purposes, one stamp or sticker to look out for is the six-pointed star.

    

The six-pointed star stamp or sticker is applied to approved equipment that has been 'rejected' as it was found on inspection to be inaccurate or not in compliance with manufacturing requirements. It also indicates that the equipment has not since been adjusted or repaired.

It is an offence to use weighing equipment bearing a six-pointed star indication for legal purposes.

It may be possible for 'rejected' weighing equipment to be adjusted or otherwise repaired and submitted to the appropriate body for requalification.

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Automatic weighing equipment

Automatic weighing machines are capable of determining or checking the weight of items without the intervention of an operator and are usually used in specialised circumstances within a production process. Their approval requirements and usage circumstances are different to non-automatic equipment and more detailed advice concerning their suitability for use can be obtained from your local Trading Standards service.

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Weights

Weights that are required to be used in conjunction with approved weighing equipment must bear an indication that they are sufficiently accurate and have been manufactured in accordance with legal requirements.

The indication will normally be found stamped into a lead plug in the base of the weight and take the form of the traditional crown stamp and date.

  

As with weighing equipment, any weights that bear a six-pointed star stamp were found to be inaccurate when they were last inspected and would be illegal for use for legal weighing purposes.

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Maintenance and use of weighing equipment

Weighing equipment can give incorrect readings because of poor practice or misuse and the following points should be noted to ensure continued accuracy:

• weighing equipment should be used on a stable, vibration free, level surface. Most equipment incorporates a level-indicator device, which must indicate that the equipment is level when in use
• weighing equipment must be correctly balanced before use, with any indicators reading zero (on electronic weighing equipment, the digital indications should not be blank prior to weighing). If the weighing equipment does not indicate zero before use, incorrect readings may be given
• strong draughts, caused by a breeze or air conditioning systems, can affect some weighing equipment, and this should be considered when selecting the position in which the equipment will be used
• the weighing pan should be kept clean and free from any debris or obstructions beneath it. Build-up of debris or other material under or adjacent to the weighing pan can interfere with the accuracy of the equipment
• regular checks of the accuracy of weighing equipment should be carried out using known quantities, such as stamped weights, to help ensure weighing equipment does not become faulty or unjust
• a record of the checks that are carried out on weighing equipment should be kept; it must identify when they are done, the action taken, the results of the checks and who carried them out, together with any necessary remedial action taken
• a maintenance contract with a weighing machine service company should be considered, especially where weighing equipment is in constant use or very high levels of weighing accuracy need to be maintained

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Trading Standards

For more information on the work of Trading Standards services - and the possible consequences of not abiding by the law - please see 'Trading Standards: powers, enforcement and penalties'.

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In this update

On 1 October 2024 the Government introduced legislation permitting the CE mark to be used indefinitely for most products. This follows the previous date of 31 December 2024 by which relevant products on sale in GB were required to use the UKCA mark.

Last reviewed / updated: October 2024

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