EIM40111 - Earnings that cannot be remitted to the United Kingdom
Section 841 IT(TOI)A 2005
Relief may be due where earnings which arise abroad and are not taxed by reference to the amount of earnings remitted to the United Kingdom, cannot be transferred to the United Kingdom because of restrictions imposed by an overseas government.
For details see SAIM1150. You should submit cases of doubt or difficulty to IPD Technical - Earnings.