Moneysupermarket was established in 1993 by Nixon, at the time a student at Nottingham University, and Duncan Cameron as a provider of off-line mortgage information to Independent Financial Advisors under the name Mortgage 2000. and in 1999 launched moneysupermarket.com providing on-line mortgage information. Since then the Business has been developed to provide credit card and personal loan information. Nixon is currently the second largest shareholder in the company, behind Capital Group.
In 2013, Nixon moved to Jersey. He has a "long term girlfriend", and also owns homes in Cornwall, Lake Windermere, Deia, Majorca, and Barbados.
In December 2015, The Guardian reported that his next share sale, on which he avoided British capital gains tax at 28% having moved to Jersey in 2013, would make him a Billionaire. In 2016 Nixon has sold his remaining 6.9% stake for £124m. In May 2017, the Sunday Times Rich List estimated his net worth at £1.176 billion.