CTM80360 | Groups: group relief: overseas permanent establishment of UK resident company - meaning of non-UK tax relief
From HM Revenue & Customs · Company Taxation Manual
For general guidance on the restriction of losses and other amounts that can be surrendered as group relief by a UK resident company that trades through an overseas permanent establishment see CTM80350.
The restriction applies where any person, other than the UK resident company, can:
otherwise get relief in respect of the loss etc. (by allowance against non-UK profits) from non-UK tax in that jurisdiction.
Where the deductibility of the loss, etc in the foreign jurisdiction depends on whether it can be deducted in the UK see CTM80365.