US President Donald Trump speaks while holding up “Simple, Fair, ‘Postcard’ Tax Filing” cards as US house speaker Paul Ryan, a Republican from Wisconsin (left) and Representative Kevin Brady, a Republican from Texas and chairman of the house ways and means committee, react during a meeting in the Cabinet Room of the White House in Washington. Photograph: Olivier Douliery / Bloomberg

Tax experts and company finance chiefs were scrambling last night to make sense of an obscure provision of the US tax reform package that could impose(...)