INTM151020 - Double taxation: concept and principles: Chargeable gains
The United Kingdom taxes its residents to Capital Gains Tax on all gains wherever they arise (TCGA92/S2(1)) but non-residents are normally not chargeable to Capital Gains Tax, unless they are carrying on a trade in the United Kingdom through a branch or agency and the gain arises on the disposal of an asset used or held in connection with the trade so carried on in the United Kingdom (TCGA92/S10). TCGA92/S276 also charges non-residents on gains from the disposal of rights and shares connected with exploration or exploitation activities in the United Kingdom or in a designated area.
Some foreign countries also charge capital gains arising in their countries to both their residents and to non-residents, so that a gain arising in one country derived by a resident of another country may be taxed twice.