At the end of March 2025, there were 474,073 premium bond accounts, the total value of which was in excess of £2.7 billion.
Over 279,475 of these accounts had no activity for more than 20 years, with the value of them standing at £16.1 million.
The figures come as the government-owned bank has faced criticism for not doing enough to find the winners, despite National Savings and Investments (NS&I) paying more than 99 per cent of the prize winners since it began in 1957.
Premium bonds prize winners should receive notifications of their winnings via text message, email or post if they have registered their details.
Some customers, however, relocate and forget to update their details.
Other bond holdings are not registered. For example, people may be unaware that they were gifted bonds as children, or they were never given the paper certificate carrying the account numbers.
Currently, there are 45,610 unclaimed prizes in the county, with the value totalling more than £1.6 million.
The highest unclaimed prize is £1,000, with the winning bank number listed as 023VK230506, which was drawn in April 1985.
The oldest unclaimed prize across the county was £25 drawn in February 1962, with the band given as 000PK557732.
READ MORE: These are the big winners of Premium Bonds in Lancashire for July 2025
READ MORE: These two Lancashire Premium Bonds numbers won £50k in August 2025 draw
NS&I retail director Andrew Westhead said the bank recognised bonds purchased before digitalisation “were much harder to trace”.
Nationally, more than £100m of premium bonds remain unclaimed, including 11 winners of £100,000 – the second largest prize available.
Since 2011, people have been able to choose to have prize money paid directly into their bank accounts.
Before that, the bank would contact prize winners and send out cheques in the post.
If you wish to find your account, NS&I’s tracing service can be contacted online, by post or over the phone if people do not have their bond number or NS&I number.