Legal for Trade Weighing in Australia: A Plain-English Guide for Load Cell Users

In Australia, if you sell or charge for goods or services by weight, the scale you use must meet trade measurement rules. In practice that means the weighing instrument must be of an approved design and must be checked and certified by a licensed person before you use it for trade. A load cell with an OIML R60 certificate is an important building block, but it is not enough on its own, because it is the complete scale that gets approved. This guide explains in plain language what “legal for trade” means, who it applies to, how load cell certificates fit in, and the practical steps to stay compliant. Rules can change, so always confirm current requirements with the National Measurement Institute.

What does “legal for trade” mean?

“Legal for trade” describes a weighing instrument that is allowed to be used where a price or charge depends on a weight. The idea is simple and fair: if you pay for 5 kilograms of potatoes, or a truck driver pays for a tonne of gravel, you should be able to trust that the scale is right. The seller should not be able to use a scale that reads heavy in their favour, and the buyer should not be short-changed.

In Australia, trade measurement is a national system run under federal law. The National Measurement Institute, usually called NMI, sets the standards, and trade measurement inspectors check that businesses follow the rules.

When does a scale need to be legal for trade?

As a rule of thumb, a scale needs to be legal for trade when the weight it shows is used to work out how much someone pays or is paid. Common examples include:

• A deli or butcher selling meat by the kilogram.
• A weighbridge weighing trucks at a quarry or grain depot to charge by the tonne.
• A recycling or scrap yard paying by weight.
• A freight company charging by the kilogram.
• A packer filling bags sold as net weight, where the labelled quantity is a trade claim.

A scale does not need to be legal for trade if it is only used internally and no price depends on it, for example monitoring how much material is left in a bin, or mixing ingredients inside your own process. Even then, many businesses choose accurate, approved equipment so they can prove quality if there is ever a dispute. If you are not sure which side of the line you fall on, ask NMI or a licensed servicing company.

The three building blocks

Think of a legal-for-trade scale as three things that must all be in place.

1. An approved design

The scale model must be of a type approved for trade use in Australia, often called pattern approval. The approval covers the whole instrument: the platform, the load cells, the indicator and how they work together. Australian requirements align closely with international recommendations from OIML, the International Organization of Legal Metrology, for non-automatic weighing instruments.

2. Components that meet the standard

The load cells, indicator and other parts used inside the scale need to meet the accuracy and performance requirements that the approved design relies on. Load cells are normally tested to OIML R60, which has accuracy classes such as C3 and C6. See load cell accuracy classes for the detail.

3. Checking and certification of the finished scale

Once installed, the scale must be verified or certified by a person licensed under the trade measurement system, using traceable test weights. The scale should then carry the required marks, and be re-checked regularly in line with the rules.

Where load cell certificates fit in

You will often see terms like OIML R60, NTEP and accuracy class C3 on load cell datasheets. Here is what they mean in plain terms.

• OIML R60: an international recommendation that sets out how load cells are tested for use in legal metrology. A certificate means the load cell was tested to defined limits for errors, temperature effects and creep.
• NTEP: a United States approval scheme for weighing devices, including load cells. NTEP approval is widely quoted on datasheets, but whether it is accepted for a particular Australian approval depends on the scale approval itself.
• C3, C6 and similar: the number shows the maximum number of scale divisions the load cell is rated for, such as 3,000 for C3 and 6,000 for C6.

Several load cells in our range carry these certifications. For example, the Revere ASC2 compression load cell is OIML R60 and NTEP certified, and the Sensortronics 60063 S-type is listed with NTEP approvals. Check each datasheet for the exact class, approvals and capacity range, because they vary by version.

The key point is that a certified load cell is a necessary ingredient, not a finished legal scale. A scale built from certified load cells but assembled without an approved design can still fail trade requirements.

A simple example: a small farm gate shop

Dani runs a farm shop that sells potatoes by the kilogram. She buys a bench scale for the counter.

1. Because customers pay by weight, the scale needs to be an approved trade scale, so she buys a model marked as approved for trade use.
2. The scale is installed on a flat, solid bench. A licensed person checks and certifies it with test weights.
3. She keeps the paperwork and the certification marks visible.
4. She checks it herself each morning with a known weight, such as a certified 1 kg test weight, and keeps a short log.
5. She has it re-checked at the required interval, and straight away if it is dropped, moved or repaired.

Dani did not pick her own load cells, because they are part of the approved scale. That is the usual route for small bench scales.

A second example: a weighbridge at a gravel yard

Tomás runs a gravel yard and is replacing a worn-out weighbridge. He charges by the tonne, so the weighbridge must be a legal-for-trade installation.

1. He chooses a weighbridge design with the right capacity and platform length for his trucks. See weighbridge load cells.
2. The supplier specifies load cells that match the approved design, such as high-capacity compression cells like the ASC2, which suit road and rail weighbridges.
3. Pits, foundations and cable runs are built correctly, with proper load cell installation.
4. After installation, a licensed person calibrates and certifies the weighbridge using traceable test weights.
5. Tomás schedules regular checks and keeps records, including after lightning storms, repairs or any change.

Who does what?

What happens if a scale is not compliant?

Using a non-compliant scale for trade can lead to warnings, penalties and the need to stop using the scale until it is fixed. It also damages customer trust. The simplest protection is to use approved equipment, keep it checked and keep records.

Practical tips for staying compliant

• Buy scales from suppliers who can show the approval for trade use.
• Do not modify an approved scale, for example by swapping the load cells for a different type, without checking the approval allows it.
• Keep the scale clean, level and free from vibration, draughts and heat sources.
• Use a known test weight for daily or weekly self-checks, and write down the results.
• Arrange re-certification when due, and after repairs, relocation or lightning damage.
• Train staff to read the scale correctly and not to overload it.

What if I only need accurate weighing, not legal for trade?

For process control, internal inventory or batching, you have more freedom. You can choose load cells on accuracy, durability and price. Even so, it is good practice to use certified, well-built load cells and to calibrate regularly. Our guides to choosing the right load cell, load cell calibration and tank, silo and hopper weighing cover these situations.

Frequently asked questions

Is an OIML R60 certified load cell the same as a legal-for-trade scale?

No. It is one required ingredient. The finished scale must be of an approved design and be certified by a licensed person.

What does C3 mean on a load cell?

It means the load cell is rated for up to 3,000 scale divisions under OIML R60. C6 is rated for up to 6,000.

Can I use an imported scale for trade in Australia?

Only if it has the necessary approval for trade use in Australia. Always check before buying.

How often must a trade scale be re-checked?

Intervals depend on the type of instrument and the rules that apply. Confirm the current requirement with NMI or your licensed servicing provider.

Do I need a legal-for-trade scale for internal stock control?

Generally not, if nobody is charged based on the reading. If you are unsure, ask NMI.

Need help with the right load cells?

Start with our complete load cell guide, then contact us with your capacity, application and approvals needed, and we will recommend suitable load cells. For OEM scale builders, see OEM load cell solutions. You can also browse the full shop.