Generally, the machines, parts of machines, and all other apparatus used for carrying on a business, but excluding stock in trade. An Annual Investment Allowance on the first £50,000 of expenditure in a financial year and capital allowances (generally 20%) for the excess over £50,000 are available for the purchase costs of machinery or plant used in a trade, profession, or vocation.
Neither machinery nor plant is defined in the Capital Allowances Act. However, in Yarmouth v France  19 QB 647 Lord Justice Lindley ruled “in its ordinary sense [plant] includes whatever apparatus is used by a business man for carrying on his business – not his stock-in-trade, which he buys or makes for sale; but all goods and chattels, fixed or movable, live or dead, which he keeps for permanent employment in his business”. Machinery and plant has been held to include a barrister's law books (Munby v Furlong  2 All ER 953 (CA), railway locomotives and carriages (Caledonian Rly Co v Banks  1 TC 487), knives and lasts used in the manufacture of shoes (Hinton v Maden and Ireland Ltd  1 WLR 875 (HL), a swimming pool (Cooke v Beach Station Caravans Ltd  1 WLR 322 (HL), decorative screens (Leeds Permanent Building Society v Procter  3 All ER 925), and a metal seagull sculpture and other items designed to create “ambience” (IRC v Scottish and Newcastle Breweries Ltd  1 WLR 1450).