More than £44million of Premium Bonds prizes of up to £100,000 in value have not been claimed, NS&I has revealed.
Among the 898,000 winners who have failed to step forward, is a woman from London who won £100,000 in February 2007 from an investment of £25.
The oldest unclaimed prize dates back to November 1957 where £25 is awaiting a man from South Yorkshire.
The Government's savings and investment vehicle is now undergoing a nationwide search to alert winners of the money waiting for them.
Over a third of the UK population has invested more than £45 billion in Premium Bonds. Every Bond is entered into the monthly prize draw to win tax-free cash prizes.
Top 5 highest unclaimed prizes in the UK
Top 5 oldest unclaimed prizes in the UK
The prizes often go unclaimed when Premium Bond holders don’t inform NS&I of a change in contact details.
Those holding a bond can help to make sure their prize doesn’t go unclaimed by having money paid directly into their bank accounts. You can check for prizes on the NS&I website.
“Prizes often become unclaimed as a result of people moving house, or forgetting that Bonds have been bought for them as a child, or executors are unaware the Bonds are held when someone dies,” said Jill Waters, NS&I’s operations manager.