Hunt under way for winners of £44 million unclaimed Premium Bonds The outstanding winnings include two individual sums worth £100,000, as well the oldest unclaimed prize, £25 won by a man from South Yorkshire in 1957. National Savings and Investments (NS&I), the Treasury-backed provider which offers the bonds, has launched an appeal to investors to check whether they could have cash unclaimed. More than a third of the UK's population has money in Premium Bonds, an investment totalling more than £45 billion. Every eligible bond is entered into a monthly prize draw and investors forgo interest in order to have the chance to win tax-free prizes. The two largest unclaimed prizes, both worth £100,000, both belong to women; one, from London, who won in 2007 - having invested just £25 - and the other, from Manchester, who won in 2010. There is also a £50,000 prize, won by a woman in Kent, in 2007, and two worth £25,000, one of which dates back to 1991. As well as the prize from 1957, there are also several outstanding from the 1960s. There is no time limit for claiming prizes and each one is held until the winner comes forward. Some of these winners may be dead, but the prize can still go to their estate. According to NS&I, many prizes go unclaimed because the winners have moved house and not notified them of their new address. As many holders are given bonds as a child, some will have forgotten they have them. NS&I has a function on their website, allowing holders to check whether they have unclaimed winnings. Customers can simply enter their bond numbers into the search box - provided they know them. Holders can also send their details and bond numbers to NS&I. Jill Waters, NS&I's operations manager, said: "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.