1) Investment gold is
(a) gold of a purity not less than 995 thousandths that is in the form of a bar, or a wafer, of a weight accepted by bullion markets or:
(b) a gold coin minted after 1800 that:
- is of a purity of not less than 900 thousandths
- is, or has been, legal tender in its country of origin; and
- is of a description of a coin that is normally sold at a price that does not exceed 180% of the open market value of the gold contained in the coin;
PDF List of gold coins Valid for 2022.
For UK since Brexit gold investment is regulated through Notice 701/21A on Investment gold coins.