Financial firms are scrambling to get to grips with new tax guidelines surrounding the use of employee benefit trusts, which are used to house the deferred share and cash components of bonuses. The changes could lead to a massive rise in tax liabilities for senior staff who borrowed money against assets locked in EBTs.

HM Revenue & Customes outlined the changes in December but the legislation is due to be finalised in today's UK Budget, but legal experts and accountants have said that banks and investment firms are still struggling to understand the rules.