V interesting 'account of profits' UK case in Blizzard v Bossland (game cheat software creator) - looks at which costs Bossland can deduct before paying it over to Blizzard. https://uk.practicallaw.thomsonreuters.com/w-021-1581
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Long and short of it = worldwide costs can't be deducted, but UK specific costs could be (e.g. costs to marketing to UK users). UK profits accounted for about 3.6% of Bossland's total business.