The Institute of Chartered Accountants in England and Wales (ICAEW) released a paper recently which suggested that the UK hasn't given proper thought to what will happen to financial reporting and accounting standards after Brexit concludes.  

The paper from the Financial Reporting Faculty of the ICAEW argues that the UK can, as a centre of global trade, exercise considerable influence over international financial reporting.  Indeed, "In many respects the UK has had a significant influence in shaping the EU accounting directives over the decades, and radical change would not be the inevitable outcome – the primary UK accounting standard, FRS 102 is, after all, a UK invention, based on international standards."