LBMA Good Delivery is the international standard maintained by the London Bullion Market Association that defines the physical, chemical and provenance requirements for gold and silver bars to be acceptable for settlement in the London wholesale market. A bar that meets the standard is described as a "Good Delivery" bar; one that does not is, in practice, unsellable to the global bullion banks at full reference price, regardless of its actual purity.

For gold, the Good Delivery specification calls for a bar of nominal weight 400 troy ounces (with an actual range of 350-430 troy ounces), minimum fineness of 995.0 parts per thousand, defined dimensions, surface finish acceptable for vaulting, and a full set of stamped marks: the refiner's mark, the bar's serial number, the year of pour, the assayed fineness, and (in modern issues) a security mark. For silver, the bar is nominally 1,000 troy ounces (range 750-1,100), minimum fineness 999.0 parts per thousand, with comparable mark requirements.

Beyond the physical specification, only refiners on the LBMA Good Delivery List may stamp bars to the standard. The list is curated by the LBMA Physical Committee and maintained against documented quality, financial solvency and (since 2012) Responsible Gold Guidance compliance. Refiners admitted to the list are required to submit reference samples annually for assay verification, and material breaches result in "former list" status (effectively a de-listing) which is publicly disclosed.

For the downstream jewellery trade, the practical effect of Good Delivery is that the LBMA-listed refiners are also the dominant suppliers of casting grain and sheet, so a jeweller buying refined gold or silver from a major refinery is buying material that traces back to the same bar pool that clears in London. This is the structural reason why "LBMA Good Delivery" appears on so many supply chain disclosures.