US President Donald Trump’s proposal to simplify and cut business and individual tax rates briefly sent shares of tax preparer H&R Block into a tailspin on Wednesday.

The stock went from a gain of 1.4 per cent to trade 1.8 per cent lower immediately after Mr Trump’s top economic team unveiled their plan for what what they called “a once in a generation opportunity” to overhaul the US tax regime.

The shares regained some of its composure and rallied to trade down 0.1 per cent at $24.21 as investors expressed scepticism over whether the proposed reform – which among other things will see the corporate tax rate from from 35 to 15 per cent – will garner enough support from lawmakers to make it through Congress.

Intuit, the $30bn company behind the popular tax preparation software TurboTax, was down 2.2 per cent. The stock has been trading lower all day – although it remains up nearly 12 per cent over the past year.

Liberty Tax, another tax service provider, also stumbled. It gave up a 1 per cent gain to trade down 0.7 per cent at $14.20.