In 1798 at the age of 21, he settled in Manchester and established a business in textile trading and finance, later moving to London and making a fortune in trading Bills of Exchange. Through establishing a network of agents, couriers and shipppers he was able to provide funds to the armies of the Duke of Wellington in Spain and Portugal. In 1818 he arranged a £5 million loan to the Prussian government and the issuing of bonds for government loans formed a mainstay of his bank’s business. He gained a position of such power in the City of London that by 1825-6 he was able to supply enough coin to the Bank of England to enable it to avert a liquidity crisis.
He set up his London business, N M. Rothschild and Sons at New Court in St Swithin's Lane where it trades today, and purchased a country house at Gunnersbury Park near Acton in western London.
By the time of his death in 1836 he had secured the position of the Rothschilds as the preeminent investment bankers in Britain and Europe. His son Lionel Rothschild (1808-1879) continued the family business in England.