CTM04020 | Corporation Tax: trading losses: general: entitlement to relief
From HM Revenue & Customs · Company Taxation Manual
A company is only entitled to relief () for losses incurred while the company carrying on the trade is within the charge to CT in respect of that trade. A company is within the charge to CT if it is:
resident in the UK, or
not resident in the UK but carrying on a trade in the UK through a branch or agency.
So, if a non-resident company trading abroad:
becomes resident in the UK on a particular date, and
becomes chargeable to CT in respect of its trade from that date,
no relief from CT is allowed for any losses incurred earlier than that date.
A company not resident in the UK but trading in the UK through a branch or agency may only get relief for losses incurred by that branch or agency.