Premium Bond

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An ERNIE money box.

A Premium Bond is a Lottery Bond issued by the United Kingdom government's National Savings and Investments agency. The bonds are entered in a regular prize draw and the government promises to buy them back, on request, for their original price. The bonds were introduced by Harold Macmillan in his 1956 budget.

The government pays interest on the bond (pegged at 1.3% in October 2013). But instead of the interest being paid into individual accounts, it is paid into a prize fund from which a monthly lottery distributes tax-free prizes, or premiums, to those bond-holders whose numbers are selected randomly. The machine that generates random numbers for the lottery is called ERNIE, for Electronic Random Number Indicator Equipment.[1] There are many different prizes ranging from £25 to the top prize of £1,000,000 (between 2005 and 2009, there were two £1m prizes each month and the minimum prize was £50, but prizes were reduced after the large 2009 drop in interest rates. A 2nd £1m prize is to be re-introduced in August 2014). Investors can purchase bonds at any time; bonds need to be held for a full calendar month after the month in which they are bought, e.g. purchase in January, eligible for March. Numbers are entered each month, with an equal chance of winning any prize, until the bond is cashed in.

The prize draw is conducted so that the winners of the jackpot can be notified on the first working day of the month, although the actual date of the draw varies for administrative reasons. The online prize finder[2] is updated by the third or fourth working day of the month.

From 1 January 2009 the odds of winning a prize for each bond number held was 36,000 to 1. In October 2009, the odds returned to 24,000 to 1 with the prize fund interest rate increase.[3] The odds reached 26,000 to 1 by October 2013. Around 23 million people own Premium Bonds,[citation needed] over one third of the UK population. Each person may own up to £40,000 in Premium Bonds. Bonds can now be purchased by the £10 after the first £100, with a value of £1 per bond and a minimum purchase of 100 bonds (or 50 bonds when paying by standing order). When they were first introduced in 1957 they were very popular – perhaps because the only other similar games of chance available to the general public were the football pools; the National Lottery did not exist until 1994. In the Republic of Ireland, a similar investment scheme called Prize Bond also originated in early 1957.


Premium Bonds were first introduced by Harold Macmillan in his budget of 17 April 1956,[4] with the aim of controlling inflation[5] and to encourage people to save in the period after the war.[6] On 1 November 1956, at a ceremony in front of the Royal Exchange in the City of London, The Lord Mayor of London, Alderman Sir Cuthbert Ackroyd bought the first bond from the Postmaster-General, Dr. Charles Hill for £1. Councillor William Crook, the Mayor of Lytham St Anne's, bought the second. Premium Bonds were based in St Annes-On-Sea until the late 1990s when they moved to larger buildings in Blackpool.[7]

Premium Bond odds[edit]

In December 2008, NS&I dropped significantly the interest rate (and therefore the odds of investors winning a prize) due to the corresponding significant drop in the Bank of England base rate during the "credit crunch", leading to strong criticism from members of parliament, financial experts, and holders of premium bonds; many claimed that Premium Bonds were now "worthless", and somebody with the maximum £30,000 invested who has "average luck" would win only 10 prizes per year compared to 15 in the previous year.[8][9] Investors with smaller although still significant amounts will probably fail to win anything at all.

Based on odds as of February 2014 of 1/26000,[10] the expected number of prizes for someone holding the maximum of £30,000 worth of bonds is 13.8 per year (The calculation is 1/26000 x 12 (draws per year) x 30,000 (number of bonds held)).

According to the Premium Bond Probability Calculator[11] on which updates the latest odds following each monthly draw, the odds of winning a prize as of February 2014 are:

Prize fund distribution[edit]

Similar prize schemes operate in other countries, for instance this Premium Prize Bond certificate from India.

The size of the prize fund on offer is equal to one month's interest on all bonds eligible for the draw. The annual rate of interest is set by NS&I and was 1.35% as of August 2014. The following table lists the distribution of prizes on offer in the August 2014 draw.[12]

Prize bandPrize valueEstimated number of prizes
Higher value£1,000,0002
7% of the prize fund£100,0004
Medium value£1,0001110
5% of the prize fund£5003,330
Low value£10015,211
88% of the prize fund£5015,211
Total value (August 2014 - estimated)£55.5m1,898,030



ERNIE (which stands for Electronic Random Number Indicating Equipment) is a hardware random number generator. The first ERNIE was built at the Post Office Research Station by a team led by Sidney Broadhurst. The designers were Tommy Flowers[13] and Harry Fensom.[14] It was unveiled in 1957,[1] and generated its bond numbers based on the signal noise created by a bank of neon tubes. ERNIE 1 is currently on display at the Science Museum in London.

ERNIE 2 replaced the first ERNIE in 1972.[1]

ERNIE 3 was introduced in 1988 and was the size of a personal computer;[1] at the end of its life it took five and a half hours to complete its monthly draw.

In August 2004 ERNIE 4 was brought into service in anticipation of an increase in the number of prizes to be allocated each month from September 2004.[1] ERNIE 4 was developed by LogicaCMG, is 500 times faster than the original ERNIE and generates a million premium bond numbers an hour; these are then checked against a list of valid bonds to determine the winning bonds before any prizes are awarded. By comparison, the original ERNIE generated 2000 numbers an hour and was the size of a van.[1]

ERNIE 4 uses thermal noise in transistors as its source of entropy for generating true random numbers; the original ERNIE used a gas neon diode. Pseudorandom numbers, often called simply random, can be recreated by anybody who knows the algorithm used to generate them as they are produced in a deterministic way; true random numbers cannot. The randomness of ERNIE's numbers derives from the inherent and unavoidable random statistical fluctuations in the physical processes involved. ERNIE's output is independently tested each month by an independent actuary appointed by the government, and the draw is only valid if the output passes tests that indicate it is statistically random.

ERNIE, anthropomorphised in early advertising, regularly receives cards and letters from the general public. It is the subject of the song "E.R.N.I.E." by the band Madness, from the 1980 album Absolutely.

Premium Bonds in other countries[edit]

Premium Bonds (under various names) exist or have existed in various countries. Common variations compared to UK Premium Bonds include:

Notes on specific countries:

Scientific evidence[edit]

Two financial economists, Lobe and Hoelzl, have analysed the main driving factors for the immense success of Premium Bonds. One in three Britons invest in Premium Bonds. The thrill of investment is significantly boosted by enhancing the skewness of the prize distribution. Using data collected over the past fifty years they find that the bond bears relatively low risk by conventional risk measures.[21]

Aaron Brown discusses premium bonds in comparison with equity-linked, commodity-linked and other "added risk" bonds.[22] His conclusion is that it makes little difference, either to an investor or from a theoretical finance perspective, whether the added risk comes from a random number generator or a financial security price.


To check whether you have won go to the National Savings[23] Premium Bond Prize Checker. It will show you the most recent draw by default; however you can choose to see if you have won anything in the past 6 months or if you have any unclaimed prizes. Older winning numbers (more than 18 months old) can also be checked in the[24] London Gazette Premium Bonds Unclaimed Prizes Supplement.


  1. ^ a b c d e f "The history of ERNIE and Premium Bonds". National Savings and Investments. Retrieved 28 March 2011. 
  2. ^ "Premium Bonds prize checker". National Savings and Investments. Retrieved 28 March 2011. 
  3. ^ "Higher payouts from Premium Bonds". BBC News. 16 September 2009. Retrieved 14 January 2010. 
  4. ^ Horne, Alistair (1989). Macmillan 1894–1956, volume I. London: Macmillan. p. 383. ISBN 0-333-27691-4. 
  5. ^ "Fifty years of Premium Bonds". This Is Money. Associated Northcliffe Digital Ltd. Retrieved 19 January 2008. 
  6. ^ "The History of Premium Bonds". This Is Money. Associated Northcliffe Digital Ltd. Retrieved 7 April 2009. 
  7. ^ "The history of Premium Bonds". NS&I. Retrieved 7 April 2009. 
  8. ^ Butterworth, Myra; Wallop, Harry (5 December 2008). "Savings". London: Telegraph. Retrieved 14 January 2010. 
  9. ^ Jones, Rupert (6 December 2008). "Now bond prizes are at a premium | Money". London: The Guardian. Retrieved 14 January 2010. 
  10. ^ "NS&I Premium Bonds". Retrieved 10 February 2014. 
  11. ^ "Premium Bond Calculator". Retrieved 30 July 2007. 
  12. ^ "NS&I Premium Bond prize draw details". Retrieved 19 August 2014. 
  13. ^ "BBC Inside Out – Premium Bonds". Retrieved 14 January 2010. 
  14. ^ Colossus: the secrets of Bletchley ... – Google Books. Retrieved 14 January 2010. 
  15. ^ For sources, refer to the main Prize Bond article
  16. ^ "Swedish premium bonds, English summary". Swedish Government. Retrieved 12 September 2013. 
  17. ^ "List of outstanding Swedish Premium bond series". Swedish Government. Retrieved 12 September 2013. 
  18. ^ "Redeeming of Premium Bonds (in Danish)". Danish Government. 19 November 2012. Retrieved 12 September 2013. 
  19. ^ "Proclamation on renewal of two State Premium Bond Loans". Danish Minister of Finance. 18 December 1987. Retrieved 12 September 2013. 
  20. ^ "Law authorizing the issue of domestic state loans". Queen of Denmark and Danish Parlament. 28 March 1984. Retrieved 12 September 2013. 
  21. ^ "SSRN-Why are British Premium Bonds so Successful? The Effect of Saving With a Thrill by Sebastian Lobe, Alexander Hölzl". 19 March 2008. SSRN 992794. 
  22. ^ Aaron Brown, The Poker Face of Wall Street, John Wiley & Sons, 2006.
  23. ^ "Premium Bond Prize Checker". Retrieved 10 April 2012. 
  24. ^ "London Gazette Unclaimed Prizes supplement". Retrieved 10 April 2012. 

External links[edit]