UK Prime Minister David Cameron has announced a referendum on whether Britain should remain in the European Union to be held on Thursday 23 June. This article is designed to be an easy-to-understand guide - and a chance to ask other questions, a selection of which we'll be answering at the bottom of the page.
Big business - with a few exceptions - tends to be in favour of Britain staying in the EU because it makes it easier for them to move money, people and products around the world. BT chairman Sir Mike Rake, a recent CBI president, says there are "no credible alternatives" to staying in the EU. But others disagree, such as Lord Bamford, chairman of JCB, who says an EU exit would allow the UK to negotiate trade deals as our country "rather than being one of 28 nations". Many small and medium-sized firms would welcome a cut in red tape and what they see as petty regulations. The British Chambers of Commerce says 55% of members back staying in a reformed EU.