Nearly £500 million has been recovered in the past five years and returned to account holders after lying dormant in forgotten funds.
The funds were located through tracing services run by the financial industry, following the launch of the My Lost Account service in 2008.
Around 315,000 people have used the service and 580,000 search applications have been made, said operators.
The service allows customers to trace funds held in accounts in banks, building societies and National Savings and Investments.
"Even small amounts of money can help with the costs of day-to-day living, so it's important people keep a track of their savings," said NS&I's retail customer director John Prout.
NS&I has reunited customers with more than £445m through its tracing service and My Lost Account, which is run by NS&I, British Bankers' Association and the Building Societies Association.
The BBA and BSA received 400,000 applications, returning £200m to customers.
"During these tough economic times every penny counts," said Brian Morris, the BSA's head of savings.
"We fully understand the importance of the scheme and will do all we can to ensure as many people as possible become aware of this free and easy to use service."