Britons have lost millions of pounds collectively "down the back of the nation's sofa" through dormant bank accounts and unclaimed pension savings and Premium Bond prizes, research from Which? has found.
The consumer group said estimates show the nation is sitting on £51 million in unclaimed Premium Bond prizes, up to £1 billion in dormant bank accounts and £400 million in unclaimed pension savings - equating to £54 for every UK household.
A survey of more than 1,300 Which? members in February found 10% believe they have lost track of Premium Bonds, 8% think savings have gone astray and 3% have untraced pension savings.
Which? said that while people can reclaim their lost money, it is worth noting that money from dormant bank accounts is donated to charity after 15 years.
It said typically, a current account will become dormant after a year of no activity and a savings account will become dormant after three years of no activity.
Which? said the provider will write to the customer asking if they want to keep the account open and if there is no reply the account will be marked as dormant.
Its research found National Savings and Investments (NS&I) will not deactivate Premium or Children's Bonds without a customer's authority, but if NS&I does not have someone's up-to-date contact details they could miss prize notifications.
Which? highlighted a free service at mylostaccount.org.uk, which helps people trace their account or savings.
The website is administered by NS&I, the Building Societies Association and the British Bankers' Association.
Which? said the more information people can provide about their account, the more likely it will be found, such as details of the branch where the account was held, the address the person lived at when they used the account and any passbooks.
The consumer group said if a bank cannot find someone's account, but they are convinced it does exist, the consumer could go to the Financial Ombudsman Service (FOS) which resolves disputes between people and financial firms.
Meanwhile, people looking for help with lost pensions could try the Pension Tracing Service - at gov.uk/find-lost-pension - or someone at their former employer.
The Pensions Advisory Service - pensionsadvisoryservice.org.uk - can also offer help.