The purpose of hallmarking is to protect buyers of precious metal items against fraud. The hallmark is a mark which shows that the item has been independently tested and verified as matching its description, and conforming to all legal standards of purity or fineness of the metal.

All items (over certain weights) sold in the UK and described as being made from gold, silver, platinum or palladium must have a legally recognised hallmark. The law is set out in the Hallmarking Act 1973 (which has been amended and updated on various occasions).