INTM169080 - UK residents with foreign income or gains: capital gains tax: Remittance basis
An individual who is resident or ordinarily resident but not domiciled in the UK and who makes a chargeable gain on the disposal of an asset situated outside the UK is only liable on the amount of the gain received in the UK (TCGA92/S12 see CG25300 onwards). When such an individual is chargeable on the gain received in the UK and claims credit for foreign tax charged on the same gain, the liability in the UK will be on the sum of the amount remitted to the UK plus the foreign tax attributable to the amount remitted.
Any difficulty in determining the correct addition for the foreign tax, should be referred to Personal Tax International (part of Charity, Assets & Residence).