The Unclaimed Assets Register, set up last year to find lost money, says there is up to £8bn unclaimed in various accounts and policies across Britain.
Many people move home without telling former employers holding pension funds for them or life offices in which they hold shares.
Untapped pension funds account for £2 billion of the unclaimed £8 billion. The rise of personal pensions means that many people have contributed to more than one policy.
A further £750 million lies in life insurance policies. Research last year indicated that 20 per cent of policyholders had no idea when their policy matured. Life insurers do not themselves search for people whose policies have matured.