The British decimal half penny (or "halfpenny") coin (½p) was introduced in February 1971, at the time of decimalisation, and was worth one two-hundredth of a pound sterling. Thus it had the rare distinction of being a non-decimal coin in a decimal currency system. It was also ignored in banking transactions, which were carried out in units of 1p.
The decimal half penny had the same value as 1.2 pre-decimal pence, and was introduced to enable the prices of some low-value items to be more accurately translated to the new decimal currency. The possibility of setting prices including an odd half penny also made it more practical to retain the pre-decimal sixpence in circulation (with a value of 2½ new pence) alongside the new decimal coinage.
The half penny coin's obverse featured the profile of Queen Elizabeth II; the reverse featured an image of St Edward's Crown. It was minted in bronze (like the 1p and 2p coins). It was the smallest decimal coin in both size and value. The size was in proportion to the 1p and 2p coins. It soon became Britain's least favourite coin. The Treasury had continued to argue that the half penny was important in the fight against inflation (preventing prices from being rounded up); however in 1984 the halfpenny was issued by the Royal Mint only in mint and proof sets, and the coin was demonetised and withdrawn from circulation in December 1984.
The decimal half penny tended to be pronounced as it is spelled, in contrast to the pre-decimal halfpenny, which was always pronounced "hayp'nny".
During the existence of the denomination, a total of 4,128,833,690 (4.1 billion) half penny coins were issued, counting proofs and coins in mint sets.