UK Gold Hallmark Guide: What the Marks Mean and How to Check Yours

A gold hallmark in the UK is a set of tiny stamped marks, usually on the inside of a ring's band, that confirm an independent Assay Office has tested the metal and verified its purity. It's not a maker's logo or a decoration: it's a legal guarantee, and by law any gold item sold in the UK over 1 gram must carry one.

What each mark actually tells you

A full UK hallmark carries up to five marks, though only three are compulsory. The sponsor's mark identifies who submitted the piece for testing. The millesimal fineness mark shows purity as parts per thousand: 375 for 9ct gold, 585 for 14ct, and 750 for 18ct, corresponding to 37.5%, 58.5% and 75% pure gold. The Assay Office mark shows which of the UK's four assay offices (London, Birmingham, Sheffield or Edinburgh) tested the piece. Together, these three marks are what the law requires; a date letter and a traditional fineness symbol are usually added too but aren't compulsory.

Why this matters more than most buyers realise

Hallmarking law in the UK, the Hallmarking Act 1973, exists specifically because gold purity can't be verified by looking at or weighing a piece; without independent testing, "18ct gold" is just a claim. The hallmark is what turns that claim into a legally checked fact. Any UK jeweller selling gold jewellery over the weight threshold without a proper hallmark is not meeting their legal obligation, regardless of what the item is described as.

How to find and read the hallmark on your own jewellery

Look on the inside of a ring band, the clasp of a bracelet or necklace, or the back of an earring stud: hallmarks are stamped small enough not to be visible from the front. A jeweller's loupe or a phone camera's macro or zoom function makes them far easier to read than the naked eye. If you can make out a three-digit number (375, 585 or 750) next to a small shield-shaped Assay Office symbol, that's your purity and testing confirmation.

What it means if you can't find one

A missing hallmark on gold jewellery over 1 gram is a red flag, not a minor omission: it means the purity claim has never been independently checked. This applies whether the piece came from a market stall or a well-presented online shop; a professional-looking website doesn't substitute for a hallmark. If a seller can't explain which Assay Office tested a piece, treat the gold purity claim as unverified until you can get it checked.

Frequently asked questions

Is hallmarking a legal requirement in the UK?

Yes, for gold items over 1 gram, under the Hallmarking Act 1973. It's illegal to describe an unhallmarked piece above that weight as a specific gold purity.

What does 375, 585 and 750 mean on a gold hallmark?

These are millesimal fineness numbers showing purity per thousand: 375 is 9ct gold (37.5% pure), 585 is 14ct (58.5%), and 750 is 18ct (75%).

Where is the hallmark usually stamped?

Inside a ring band, on a bracelet or necklace clasp, or on the back of an earring stud: always somewhere not visible when the piece is worn.

How can I check a hallmark if I can't read it with my eyes?

Use a jeweller's loupe or your phone's macro or zoom camera function. The marks are stamped small deliberately, but they're legible at close range with magnification.

What should I do if my jewellery has no hallmark?

If it's gold and over 1 gram, treat the purity as unverified. You can have it independently tested at a UK Assay Office if you want certainty before wearing or insuring it.

Every piece of gold jewellery we make is hallmarked to UK Assay Office standard as standard practice, not an optional extra. Browse the engagement rings collection or read our 9ct vs 18ct gold guide for more on choosing purity.