Capital allowances on commercial HVAC: what businesses can claim

This page summarises HMRC's published rules on capital allowances for heating, ventilation and air conditioning; it is not tax advice, so check how they apply to your business with an accountant before committing to a project.

Are air conditioning and heating systems integral features?

Usually, yes. Capital allowances let a business deduct some or all of the value of qualifying plant and machinery from its profits before tax. GOV.UK lists "integral features" as a category of plant, and the list includes space and water heating systems and air-conditioning and air cooling systems.

HMRC's Capital Allowances Manual gives the legal definition. One of the listed integral features is "a space or water heating system, a powered system of ventilation, air cooling or air purification, and any floor or ceiling comprised in such a system". HMRC adds that these terms are not specifically defined, so they take their ordinary meaning, and that only assets on the list count as integral features.

Some details matter on an HVAC project:

• Plenum floors and ceilings. A plenum floor or ceiling whose main purpose is to work as part of the heating or air conditioning system can qualify as part of the integral feature. A new false ceiling that simply hides wiring and pipes does not qualify.
• Ductwork. HMRC says ducting follows the tax treatment of the system it supports. Ducting that serves only a computer system could be main pool expenditure, and ducting shared between systems should be apportioned on a fair and reasonable basis.
• Building alterations. GOV.UK counts alterations to a building made to install plant as plant and machinery, but not repairs.

Which pool does HVAC spending go into?

Expenditure on providing or replacing integral features is special rate expenditure. That matters because the writing down allowance in the special rate pool is 6% a year, compared with 14% in the main pool from April 2026 (18% before). HMRC's manual confirms that if writing down allowances are claimed on integral features, they must be at the special rate rather than the main rate.

In practice, a business rarely has to rely on 6% a year for a new system, because the Annual Investment Allowance and, for companies, the 50% first-year allowance can give much faster relief. The pool matters most for spending above those allowances and for unincorporated businesses.

How does the Annual Investment Allowance apply?

The Annual Investment Allowance (AIA) lets a business deduct the full value of qualifying plant and machinery from its profits before tax, up to the AIA amount, which GOV.UK currently gives as £1 million. HMRC's manual confirms that businesses can use the AIA for expenditure on integral features, so it is often the first allowance to consider for an HVAC project.

Points to watch:

• Timing. The AIA can only be claimed in the period the item was bought. GOV.UK treats the purchase date as the date the contract was signed if payment is due within less than four months, or the date payment is due if it is more than four months later.
• Accounting periods. A business gets a new allowance for each accounting period, adjusted if the period is longer or shorter than 12 months.
• Groups. Two or more limited companies controlled by the same person get only one AIA between them.
• Spending above the limit. Any amount above the AIA can go to first-year allowances or writing down allowances, and a single large item can be split between them.

Can a company claim full expensing on air conditioning?

Not normally. Only companies can claim full expensing and the 50% first-year allowance, on plant and machinery bought from 1 April 2023 that is new and unused and is not a car. GOV.UK's eligibility guidance then splits the two: for main rate plant, a company can deduct all of the cost under full expensing; for special rate plant, it can deduct half of the cost under the 50% first-year allowance and add the balance to the special rate pool in the following period.

Because air conditioning, powered ventilation and heating systems are usually integral features, and integral features are special rate, the 50% first-year allowance is the relevant one. GOV.UK also notes that special rate expenditure may qualify for the AIA. The newer 40% first-year allowance, for plant bought on or after 1 January 2026, is limited to items that qualify for the main rate, so it does not normally apply to integral features either.

Allowance	Who can claim	Typical use on HVAC integral features
Annual Investment Allowance	Most businesses, up to the annual limit	Yes: full cost in the year of purchase, within the limit
50% first-year allowance	Companies only, new and unused plant	Yes: half the cost in year one, balance to the special rate pool
Full expensing	Companies only, new and unused plant	No: main rate plant only
40% first-year allowance	New and unused plant bought on or after 1 January 2026	No: main rate plant only
Writing down allowance	Any business	Yes: 6% a year in the special rate pool

One further case is worth knowing about. Companies can claim 100% first-year allowances on plant and machinery for use in a special tax site in a UK Freeport or Investment Zone, which can change the picture for HVAC in qualifying buildings on those sites.

What changes when an existing system is replaced?

Replacement projects raise the question of whether spending is a capital cost or a repair. HMRC's rule for integral features is that if the spending is the whole, or more than 50%, of the cost of replacing an integral feature, either at once or within any 12-month period, it is treated as capital expenditure on a replacement. That expenditure then counts as special rate expenditure, and it cannot also be deducted as a revenue expense.

The 12-month window is designed to stop businesses splitting a replacement across accounting periods to keep each part below half. HMRC's examples show that a replacement paid in two instalments either side of a year end can still be treated as one capital replacement, while a genuinely partial job, below half of the whole-system replacement cost, stays outside the rule. HMRC also says there is no statutory obligation to obtain more than one quote or estimate when judging the replacement cost.

Other practical points:

• Repairs that are not capital are claimed as business expenses, or deducted as a business cost by a limited company.
• Selling or disposing of plant after claiming full expensing (main-rate plant) or the 50% first-year allowance means working out a charge to add to taxable profits, so keep a record of what was claimed on each item.
• When buying a building, the buyer and seller must agree the value of the fixtures for the buyer to claim for them.

The quickest way to make all of this workable is an itemised quotation that separates integral features, any main-rate items, builders' work and repair work, so an accountant can allocate each line. Readers comparing projects can request quotes through the site's form and ask for that breakdown, and the commercial HVAC cost pages show what typically drives a project's price.

How are capital allowances claimed?

Allowances are claimed on the tax return: a Company Tax Return for limited companies, which must include a separate capital allowances calculation, or the Self Assessment or partnership return for unincorporated businesses. The AIA and the first-year allowances must be claimed in the accounting period the item was bought. Anything not claimed that way can be claimed later through writing down allowances while the business still owns the item.

Capital allowances are not the only funding route for an HVAC project. The grants and funding guide covers other options, and the article on how to fund a commercial HVAC upgrade compares them side by side.

Sources

• Claim capital allowances (overview, what you can claim on, annual investment allowance, first-year allowances, full expensing for main-rate plant, 40% first-year allowance, how to claim), HM Revenue and Customs (GOV.UK), checked 20 October 2026
• Check if you can claim full expensing (main-rate plant) or 50% first-year allowances, HM Revenue and Customs (GOV.UK), checked 20 October 2026
• Work out your capital allowances: rates and pools, HM Revenue and Customs (GOV.UK), checked 20 October 2026
• Capital Allowances Manual CA22320, CA22330 and CA22340, HM Revenue and Customs (GOV.UK), checked 20 October 2026

Common questions

Can a landlord claim capital allowances on air conditioning in a let building?

GOV.UK says a business can claim if it rents or owns the building, but only the person who bought the item can claim. Leasing rules differ for full expensing and the 50% first-year allowance, which exclude plant bought to lease to someone else unless it is background plant or machinery within a building.

Is a heat pump an integral feature?

A heat pump that heats a building forms part of a space or water heating system, which is on HMRC's integral features list. HMRC says these terms take their ordinary meaning, so the same special rate treatment usually applies.

Do servicing and repairs count for capital allowances?

No. GOV.UK says alterations made to install plant count as plant and machinery but repairs do not, and repairs are claimed as business expenses. The exception is a replacement of more than half of an integral feature within 12 months, which HMRC treats as capital.

What if an HVAC project runs across two accounting periods?

The AIA and first-year allowances are claimed in the period the item was bought, using GOV.UK's contract and payment date rules. For replacements, HMRC's 12-month test looks at the total spent on replacing the integral feature across that window, not each period separately.

Related guides

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