On 15 August 2026, the compliance deadline passed for the sixth edition of Great Britain’s Mandatory Classification and Labelling List. From that date, new or revised classifications for 46 substances became mandatory for any product newly placed on the GB market (ChemLinked, Feb 2025). For chemical suppliers, the deadline is no longer something to plan for. It is something to check against.
What Is the GB MCL List?
The GB MCL list is the Health and Safety Executive’s register of legally binding hazard classifications for specific substances on the Great Britain market. Where a substance has a mandatory classification, suppliers must apply it, regardless of their own assessment.
The sixth edition was published in February 2025 and included substances such as trimethyl borate and hydrogen sulphide. A seventh edition covering around 30 further substances followed in September 2025, with its own compliance deadline in March 2027 (REACH24H, July 2026). HSE also proposed changes to another 60 substances in January 2026. Separately, the requirement to notify HSE of classifications was removed from 21 May 2026, but that administrative change does not affect the duty to apply mandatory classifications on the label.
What Does the Deadline Mean for Existing Stock?
The deadline means that any affected product placed on the market from 15 August 2026 must carry the updated classification on its label and safety data sheet. Stock placed on the market before that date may continue through the supply chain, but new placements must comply.
That distinction matters operationally. A product filled and labelled last month with outdated hazard information cannot simply be released now. Distributors need to know which batches were placed on the market before the deadline and which were not, and that relies on accurate records rather than assumptions.
A GB MCL review also covers more than pictograms. A revised classification can change the signal word from Warning to Danger, add hazard statements, alter which precautionary statements are needed and trigger extra packaging requirements, such as tactile warnings or child resistant closures for certain hazards. Mixtures are affected as well, because suppliers must use the mandatory classification when classifying any mixture that contains the substance. A single substance change can ripple through dozens of product labels.
Why Is the Next Print Run So Important?
The next print run is where compliance becomes visible. A label reprint is the natural point to check every substance in a product against the current GB MCL list, update pictograms, signal words, hazard statements and precautionary statements, and confirm the label matches the latest safety data sheet.
Getting it wrong is expensive. A label printed with outdated hazard information becomes unusable stock the moment it is checked. Getting it right once, against the current list, avoids paying for the same label twice.
With the seventh edition deadline only months away, suppliers who review their portfolio now can combine both sets of changes into a single reprint. That is the most efficient way to stay ahead of a list that is now updated regularly rather than occasionally.