Direct answer
Under the UK average system, control the batch so average contents are not below the nominal quantity, only the permitted small proportion falls beyond the tolerable negative error, and no pack falls below twice that error. Use suitable measuring equipment, a documented sampling plan and records that show the process remained under control.
Understand the three rules
Current GOV.UK guidance describes three controls: the contents must not be less on average than the nominal quantity; the proportion below the nominal quantity by more than the tolerable negative error must remain below the permitted level; and no package may be short by more than twice the TNE.
These rules work together. A batch with a satisfactory average can still fail because one pack is excessively short, while a high target can mask an unstable process by creating unnecessary giveaway.
Set a target from measured capability
Measure filler variation using representative product, containers, temperatures, speeds and replenishment conditions. The target should provide adequate control against short packs while avoiding a blanket overfill that hides poor repeatability.
Separate tare variation from product variation and use suitable verified equipment. For liquids, consider density and the method used to convert between mass and volume.
Create a sampling and response plan
Define when samples are taken, how they are selected, which result is recorded, who reviews the trend and what triggers adjustment or hold. Include start-up, after changeover, after intervention and throughout the run.
A failed result needs a defined response: stop or adjust, identify the affected time window, increase checks, quarantine product and document disposition.
Use checkweighing as process evidence
An inline checkweigher can inspect every pack and support trend feedback, but it must be selected and validated for the pack, speed and required performance. Reject confirmation and secure reject handling matter as much as the weigh cell.
Keep challenge-test, calibration or verification, set-point, recipe and reject records according to the site’s quality system and current legal guidance.
Information to prepare
- Confirm whether the average or minimum system applies
- Calculate the correct TNE for each nominal quantity
- Measure tare and filler capability
- Set documented target and control limits
- Define sampling frequency and corrective action
- Verify measuring equipment and checkweigher performance
- Retain batch and intervention records
Weigh Fillers
Net-weight and weigh-filling routes where mass control is central to the application.
Official references
Check the current source before relying on dates, thresholds or legal duties.