The Capital Allowances Act 2001 does not define plant. Case law treats it as apparatus kept for permanent use in carrying on a business, as opposed to the premises or setting in which the business is carried on, and statute then excludes most buildings and structures while restoring specific items. A capital allowance claim stands or falls on applying both layers to the asset and the particular trade.

Is there a legal definition of plant and machinery?

No. HMRC’s Capital Allowances Manual (CA21010) confirms that the legislation does not define either word, so they take their common law meaning. On top of that, sections 21 and 22 of the Capital Allowances Act 2001 (CAA 2001) exclude most buildings, structures and works altering the ground, and section 23 carves certain items back out of those exclusions. The practical order of working is therefore:

  1. Is the item treated as plant by statute regardless of function, such as an integral feature or thermal insulation?
  2. If not, is it caught by the building or structure exclusions in sections 21 and 22?
  3. If it escapes them, or is in List C of section 23, does it function as plant under case law?

Machinery rarely causes difficulty. HMRC accepts that machines and their working parts, vehicles, lathes and computers are machinery (CA21010). The arguments are almost always about plant. For how the allowances themselves work, see capital allowances explained.

What did the courts say plant is?

The starting point is Yarmouth v France (1887), a case under the Employer’s Liability Act 1880. Lindley LJ described plant as whatever apparatus a businessman uses for carrying on his business, not his stock in trade, but all goods and chattels, fixed or movable, which he keeps for permanent employment in the business (CA21100). Three features follow:

  • it is apparatus used for carrying on the business;
  • it is not stock in trade; and
  • it is kept for permanent employment. HMRC accepts that an asset with an expected life of two years or more is durable enough, drawing on Hinton v Madden and Ireland Ltd, where shoemakers’ knives and lasts with an average life of three years were plant.

The functional test

In Benson v Yard Arm Club Ltd, a ship converted into a floating restaurant was refused allowances because it was the structure in which the trade was carried on, not apparatus with which it was carried on. Templeman LJ said he could see no distinction between a restaurant on the Thames and a fish and chip shop in Bethnal Green (CA21100). The functional test is not whether an asset has a function, since every business asset does, but whether it functions as apparatus in the business.

Where is the line between plant and premises or setting?

In J Lyons and Co Ltd v Attorney General, lamps were held to be part of the setting in which the business was carried on rather than plant (CA21110). Later cases showed the setting test is not absolute:

  • Jarrold v John Good and Sons Ltd: movable office partitions were plant because the business needed to move them as a matter of commercial necessity (CA21120). HMRC checks whether partitions have actually been moved.
  • Leeds Permanent Building Society v Proctor: decorative window screens designed to attract customers were plant.
  • CIR v Scottish and Newcastle Breweries Ltd: light fittings and decorative items in hotels and pubs were plant because creating atmosphere was part of the trade, while the electrical wiring was part of the building (CA21130). HMRC only accepts decor as plant where the trade sells ambience and the items were chosen to create it; a painting on an accountant’s office wall is not plant.

The Wimpy tests

In Wimpy International Ltd v Warland, Hoffmann J set out three questions: is the item stock in trade, is it the premises or part of the premises, and is it used for carrying on the business (CA21140). To decide whether something has become part of the premises, he suggested four factors:

  • does it visually retain a separate identity;
  • how permanently is it attached;
  • to what extent is the building complete without it; and
  • is it intended to be permanent or likely to be replaced within a short period.

These are questions of fact and degree, not hurdles. Wimpy’s replacement shop fronts, floor and wall tiles and staircases failed; murals and decorative panels passed. HMRC also notes that, under Attwood v Anduff Car Wash Ltd, assets are normally looked at piece by piece rather than treating a whole site as one item of plant (CA21160).

Which assets does statute exclude or rescue?

Lists A and B

Section 21 excludes expenditure on buildings, including assets incorporated in a building or of a kind normally incorporated, and List A items: walls, floors, ceilings, doors, gates, shutters, windows and stairs, mains services for water, electricity and gas, waste disposal, sewerage and drainage, lift shafts and fire safety systems (CA22010). Section 22 excludes structures, works altering the ground and the List B assets, including tunnels, bridges, roads, car parks, hard standings, docks and dams (CA22020). HMRC’s reading of tunnel, bridge, viaduct, cutting and similar words in List B now follows the Supreme Court decision in HMRC v SSE Generation Ltd [2023] UKSC 17 (CA22020).

Items treated as plant

Section 23(2) treats thermal insulation, personal security assets, integral features and software as plant whatever their function (CA22030).

List C

Section 23(3) saves the List C items from the exclusions, but HMRC stresses that List C does not make anything plant: each item must still pass the case law tests (CA22030). Examples include manufacturing and display equipment, kitchen and sanitary ware, computer and surveillance systems, fire and burglar alarms, movable partitions, decorative assets in hotels and restaurants, signs, swimming pools, cold stores, silos for temporary storage and groundworks carried out only to install plant. List C does not work by analogy: fixed zoo cages do not extend to kennels or stables.

Can a building or structure ever be plant?

Rarely. HMRC accepts (CA22050) that a structure can be plant if and only if it is apparatus rather than the place where the business is carried on. The leading examples are the dry dock in CIR v Barclay Curle and Co Ltd, which moved ships to and from the river, the transit grain silo in Schofield v R and H Hall Ltd, and the caravan park swimming pool in Cooke v Beach Station Caravans Ltd. These items now appear in List C. For a pool at a hotel or caravan park, HMRC allows excavation, construction and terracing, but not changing rooms or the building housing an indoor pool (CA22060).

How do the tests apply to common items?

Item Usual position Reference
Fitted kitchen or bathroom suite in a commercial building Plant (List C item 5) CA22030
Office carpets, curtains, furniture Plant if durable and used in the trade CA21200
Permanent internal walls and false ceilings Not plant CA22010, CA22320
Demountable partitions actually moved in the business Plant CA21120
Lighting and electrical system Integral feature, special rate CA22320
Car park surface or yard Not plant (List B); consider structures and buildings allowance CA22020
Artwork in a restaurant chosen to create atmosphere Plant CA21130
Artwork in a professional office Not plant CA21130

Excluded buildings and structures may instead qualify for the structures and buildings allowance. Repairs are revenue, not plant, so check capital versus revenue first.

What mistakes cause claims to fail?

  • Assuming a List C item qualifies automatically.
  • Claiming a whole fit out as one asset instead of analysing it item by item.
  • Arguing a ruling from one trade applies to another. HMRC notes (CA21135) that whether something is plant depends on the particular trade: a ship used as a restaurant is not plant, but a ship used in shipping is.
  • Buying a building without agreeing the value of fixtures with the seller. Gov.uk guidance says that if the value is not agreed, the buyer cannot claim for them.
  • Residential landlords claiming for items in a dwelling, which is blocked separately; see capital allowances for landlords.

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Reviewed by Christine Anderson, Broker, Solar Protect. Last reviewed 8 October 2026. Part of Accountapedia, the Solar Protect guide to UK tax and accounting. This page is general information, not personalised advice.