TS–006 When is a full verification test required for weighing and measuring instruments

This policy confirms when a weighing or measuring instrument, which is in use for trade, requires a full verification test to be completed.

Reference documents


Where the Mark of Verification (MOV) or sealing has been broken for the purposes of accessing an instruments calibration settings, or to alter any metrological characteristic, the instrument must be verified by performing a full verification test.

This includes, but is not limited to, replacing any of the following components that can affect the metrological characteristics of the instrument:

  • Load cells,
  • Junction boxes,
  • PEC board in the indicator, or the complete indicator
  • Flow meters and indicating device, and
  • Any calibration action that causes an instruments event-counter to increment up.

This also includes but is not limited to altering any of the following calibration functions;

  • Span adjustment
  • Zero adjustment
  • Meter alteration or a K factor adjustment


There can be instances where an instrument has the MOV removed or sealing broken to gain access to the instruments interface and upgrade the non-legally relevant software or replace hardwired auxiliary devices, e.g. a printer or secondary indicator that has no effect on the metrological characteristics of an instrument.

This activity is permitted if:

  • The MOV or sealing is removed by the Accredited Person (AP) individual or organisation that applied it
  • The action and date is recorded on the original test sheet for the instrument
  • Any existing Certificate of Accuracy is not altered or removed.

Tip Icon Blue2 NOTE

The AP reapplying the MOV must be accredited for that particular category of instrument.

Any other instance requires the prior written approval from Trading Standards or a full verification test to be performed.

Trade Measurement — Technical Policy

Policy number: TS - 006
Effective date: July 2016
Version date: December 2019
Version number: 2
Policy name: When is a full verification test required for weighing and measuring instruments
Reviewed by: Davis White, Legal Metrology Advisor and Senior Trading Standards Officer
Approved by: Phil Sorrell, Team Leader Compliance and Inspection