Of all the many restrictions on the use of corporation tax losses, one of the best known is the rules which require both a change in the ownership of a company and a major change in the nature or conduct of a trade.

Found in Corporation Tax Act 2010 (CTA 2010), Pt 14, Ch 2, this rule prevents the carry forward of pre-change-in-ownership trading losses against post-change-in-ownership trading profits.

Before the 2017 loss relief reforms, there was no need for a similar rule preventing the carry-forward of pre-change-in-ownership trading losses against post-change-in-ownership total profits because the carry-forward of trading losses against total profits was simply not permitted.