 In 1698, Duncombe was arrested and imprisoned in the Tower of London, and subsequently expelled from the House of Commons, for "contriving and advising the making of false Indorsements of several Bills, made forth at the Receipt of Exchequer, commonly called Exchequer-Bills", in other words a tax fraud.He was expelled from the House of Commons on 1 February 1698.However, at his trial, he was acquitted through a mistake in the information.