Some £15bn of unclaimed assets is lying in so-called dormant accounts. John Greenwood explains how you can detect the money you did not know you had

National Savings & Investments is on the hunt for 500,000 Premium Bond holders who have yet to claim prizes worth up to £25,000. But while unclaimed Premium Bond prizes ranging from £25,000 to £50 now add up to a total value of £30m, this is just a fraction of the estimated £15bn of unclaimed assets left forgotten in old bank savings accounts, pensions and investment products.

Digging up the past: there are ways to detect assets you've lost track of

Banks and other financial institutions are benefiting to the tune of millions of pounds from this hoard of cash, most of which is earning little or no interest for customers.

NS&I itself is holding £1.8bn of savers' cash in dormant accounts that have not been touched for 15 years, the vast majority of which is earning paltry rates of interest.

People often lose track of savings and investments because they fail to pass on their new address when they move house; savings made on their behalf when they were children have since been forgotten or they have simply died and executors have not located their accounts.

Earlier this year, a Government commission recommended that these forgotten billions should be placed in a social investment bank and then paid out to community projects throughout the UK.

The Government and financial services industry have not yet agreed on a formula for removing the assets and distributing them, but it is understood that only accounts that have been untouched for 15 years will be included.

You may be worried at the thought of your cash being paid out to a worthy cause just because you have not contacted the company looking after it for 15 years, but the industry is planning to guarantee that any individual can claim their cash in full from a financial institution no matter how long it is since contact has been made.

This time limit will not apply to pensions in any event, because they are commonly held for far longer than 15 years without contacting the provider or trustees. This new social investment bank is unlikely to be paying out cash to worthy causes until 2008 at the earliest, but if you have the flickering of a memory of an account taken out in your dim and distant past then there are ways to find out if a financial institution has something of yours buried in its books.