Premium Bonds continue to be popular, with some 23 million small investors hoping for a shot at the £1 million top prize. They were launched in 1956 by Harold Macmillan, then Chancellor of the Exchequer, as a way to control inflation and encourage saving in the post-war world. On the first day alone, £5m of bonds were sold, and the top prize in 1956 was £1,000 – about £25,000 in today’s money. But today most payouts are of a more modest £25, and the chance of winning is said to be 36,000 to one. Here's everything you need to know about Premium Bonds, when they are drawn and how much you can win. What are Premium Bonds? Premium Bonds are currently issued by the government's National Savings and Investments (NS&I) agency. The government pays interest into a bond fund from which a monthly lottery distributes tax-free prizes to bondholders whose numbers are selected randomly by a machine called ERNIE (Electronic Random Number Indicator Equipment). The idea is that rather than a stake being gambled, as in a usual lottery, it is the interest on the bonds that is distributed. For more information on Premium Bonds, head to the NS&I website How to check if you have Premium Bonds If you think there is a chance that you could have Premium Bonds, but you are not sure, there is a tracking service on the NS&I website. To check if you have any bonds you need to fill out a form with your personal details and send it off. If you do have Premium Bonds, then you will be contacted. How to check if you have won a prize An unclaimed prize is classified as one that has not been claimed within 18 months of it being won. There is no time limit to making a claim. NS&I, which runs Premium Bonds, contacts winners when they have a prize to claim, however sometimes this does not work if contact details are not up-to-date or letters get lost in the post. And sometimes people may not know that they could potentially be due a letter, having forgotten about bonds they bought a long time ago or were given as a gift. If you know you have bonds and want to find out if you are owed a prize, you can also do this on the NS&I website. To do so you need your unique holder’s number, which can be found on your bond record or by logging into your account on the NS&I website. It is a nine or 10 digit number, or an eight digit number with a letter at the end. You then need to enter this number into the prize checker and it will tell you whether you are due to claim a prize or not. You can also use your NS&I number to check if you have won a prize, but this can only be done in the app and not on the website. If you have an NS&I number, you'll find it on most communications you've had with them.If you only know your bond numbers, or have lost your documents, then the only way to find out if you have won a prize is to write to NS&I and request a bond record. When are prizes drawn? Premium Bond prizes are drawn at the start of each month. The big prize winning numbers – between £5,000 and £1million – are shared with the media first. But winners will find out the size of their fortunes when they are contacted by an NS&I worker on the day before the first working day of the month. In August, that day was Sunday 2 August.