Capital Allowances Explained: AIA, Full Expensing and Tax Relief on Business Assets

Quick answer: UK capital allowances can reduce taxable business profits when qualifying plant, machinery and other business assets are acquired. The correct claim depends on who bought the asset, whether it is new or used, the kind of asset, the acquisition date and whether Annual Investment Allowance (AIA), full expensing, a first-year allowance or writing-down allowances apply. An accounting expense and a tax deduction are not always the same thing.

What are capital allowances and who can claim them?

Capital allowances provide tax relief for certain capital expenditure. A growing business might buy a manufacturing machine, shop equipment, commercial kitchen equipment, office furniture, computers or qualifying fixtures. These purchases often create assets in the financial accounts rather than ordinary day-to-day expenditure. Capital allowances determine the tax relief instead of assuming that the accounting depreciation charge is deductible.

Companies generally claim through the Corporation Tax computation accompanying their Company Tax Return. Sole traders use their Self Assessment computation, while partnerships have separate tax treatment for partners. The availability of individual allowances varies. For example, full expensing and the 50% special-rate first-year allowance are company-only reliefs, whereas AIA may be available to several kinds of businesses. HMRC’s capital allowances overview explains the overall framework.

The practical question is not simply “can the company deduct the machine?” It is: which qualifying cost, in which period, using which statutory allowance, gives a lawful and supportable result? This matters when comparing equipment, financing and tax cash flow.

Capital allowances compared: AIA, full expensing and other reliefs

Do not stack several 100% allowances on the same expenditure. Where more than one relief is available, there may be a choice to make. AIA is not an automatic substitute for every first-year allowance, and cars are a particularly important exception. See HMRC’s full-expensing guidance and claim instructions.

The £1 million Annual Investment Allowance: how it works

AIA can allow eligible businesses to deduct the qualifying expenditure in the period of purchase up to the applicable £1 million annual limit. That does not mean HMRC pays the company £1 million, and it does not mean every business has a separate full allowance when businesses are connected or under common control.

Imagine a UK limited company buys £60,000 of qualifying manufacturing equipment in its accounting period. Assuming it is entitled to AIA and has sufficient unused allowance, it may deduct £60,000 from taxable profit. If its marginal Corporation Tax position happened to give a 25% saving on that full deduction, the illustrative reduction would be £15,000; actual savings depend on company profits, marginal relief, associated companies and other factors. The purchase itself still costs £60,000, so tax relief does not make the asset free.

AIA is particularly useful for qualifying second-hand equipment because full expensing usually requires new and unused assets. But used equipment still needs to meet the rules, with evidence of actual cost and business use. For more on the underlying tax computation, see Britvex’s Corporation Tax service.

Full expensing: when 100% can be claimed immediately

Full expensing allows companies to deduct the full cost of certain new and unused qualifying main-rate plant and machinery in the year it is acquired. It is aimed at genuine qualifying business investment, not all expenditure placed on an invoice with the label “equipment”.

For example, a company investing £120,000 in eligible new machinery might have £120,000 qualifying for full expensing, subject to the legislation and facts. If the company had no adequate taxable profits in the period, the full deduction is still relevant to its tax computation but cannot automatically be described as an immediate cash refund. Loss relief, group position and future profitability need their own examination.

The company should record supplier invoices, delivery dates, the contract, capitalisation in the accounts, use of the machinery and whether anyone else has claimed the asset. On disposal, special balancing charge rules can apply; advisers must not describe full expensing as a tax benefit with no future consequences.

The 40% first-year allowance and the 14% main pool rate

These two details make this guide particularly important to UK businesses reviewing investments during 2026. HMRC announced a 40% first-year allowance for qualifying expenditure on or after 1 January 2026, alongside the reduction of the main pool writing-down allowance rate from 18% to 14% from 1 April 2026 for Corporation Tax and 6 April 2026 for Income Tax businesses. A period straddling those commencement dates can need a blended rate. <a href=”https://www.gov.uk/government/publications/new-first-year-allowance-and-main-rate-of-writing-down-allowances/capital-allowances-new-first-year-allowance-and-reducing-main-rate-writing-down-allowances”>HMRC’s policy note</a> explains this change.

The 40% allowance may be relevant when an asset cannot qualify for full expensing or AIA, including some otherwise eligible leasing situations. It should not be presented as an across-the-board 40% write-off on used machinery, cars or any business purchase. A tax computation should separate the allowance claimed upfront from the remaining eligible pool balance.

Illustration: A £50,000 asset that genuinely qualifies for the 40% allowance could obtain a £20,000 first-year deduction, with the remaining £30,000 treated under the applicable pool rules. A 40% deduction is not a 40% reduction in the tax bill: the eventual tax effect depends on the taxpayer’s tax rate and taxable profit.

What qualifies as plant and machinery?

Typical potentially qualifying assets include commercial machines, IT hardware, printers, tools, office fixtures, furniture and eligible building-integrated installations. But the tax classification of alterations to premises, electrical systems, integral features and structures can be complex.

Businesses operating from leased premises should pay particular attention to who incurred the qualifying cost and who has rights over the installations. Keep a separate fixed-asset register and reconcile it with the accounting ledger.

Cars, vans and electric vehicles: avoid mixing the rules

Cars have their own capital-allowance rules. A qualifying new and unused zero-emission car may obtain a 100% first-year allowance where the statutory conditions are met, whereas second-hand electric cars and petrol/diesel cars follow different writing-down rules. The treatment of vans is not identical to passenger cars. Full expensing excludes cars. Refer to HMRC’s business-car guidance.

A business considering a company car must also examine personal Benefit in Kind, employer Class 1A National Insurance, charging costs and VAT. Those are not answered merely by a Corporation Tax capital-allowance deduction. We cover that separately in Britvex’s dedicated company-car guide on Britvex.co.uk.

Buying outright, hire purchase or leasing

How an asset is financed can affect the capital-allowance position. A purchase funded by a normal business loan is generally examined as an asset acquisition with separate finance costs. Hire purchase has specific rules: relief may be available on eligible total purchase cost when the asset is brought into use under the agreement, excluding finance interest. An operating lease may instead involve deductible rental expenses, with different capital-allowance implications and possible lessor claims.

Do not choose a finance product solely from an advertised “100% tax relief” message. The headline may omit interest, ownership, contract structure, VAT and the timing of cash payments. For an important acquisition, obtain a written accounting and tax treatment before signing.

Three practical capital allowance scenarios

Scenario A — New machine for a profitable limited company

A manufacturer buys a new £90,000 qualifying machine. Depending on the facts, AIA or full expensing may be relevant. The company’s tax computation should choose the correct relief without claiming both. If full relief is available, the deductible amount may be £90,000; a 25% illustration gives £22,500 less Corporation Tax, but this assumes the same marginal effect applies throughout.

Scenario B — Second-hand office equipment

An SME buys £14,000 of used qualifying office equipment. New-and-unused first-year relief may not apply, but AIA could be considered if the conditions and available annual limit are satisfied. The invoice, business purpose and actual ownership must be evidenced.

Scenario C — Mixed building refit

A retail company spends £80,000 on a shop refit. Some items could be qualifying fixtures or plant, some could be building works, and some could be repairs. Assigning one capital-allowance treatment to the entire invoice risks overstating the claim; obtain an itemised contractor schedule and classify each component.

Capital allowances in annual accounts, tax computations and CT600

The financial statements normally recognise the asset and accounting depreciation, while the tax calculation adjusts for the depreciation and applies lawful capital allowances. The distinction is essential: a company can have a £10,000 depreciation expense in its accounts but a very different capital-allowance deduction in its tax return.

Your accountant should maintain an asset-by-asset schedule showing date, cost, supplier, tax classification, selected allowance, balancing charges and written-down value. Britvex links Bookkeeping, Annual Accounts and Corporation Tax so the tax calculation uses the underlying records.

HMRC has indicated that its Corporation Tax online service will be updated later to provide dedicated boxes for the new 40% allowance; interim CT600 box guidance is available in its service updates. A new allowance does not remove the requirement to use the correct currently available filing procedure.

A capital-allowance checklist before buying an asset

1. Identify the purchaser and the entity that will use and own the asset.
2. Obtain a supplier quotation with items separately specified.
3. Record whether each item is new, used, a car, special-rate plant or ordinary main-rate plant.
4. Check available AIA and any connected-business restrictions.
5. Compare AIA, full expensing, the 40% allowance and writing-down allowances, where each is legally available.
6. Forecast the company’s taxable profits and available losses before describing any cash saving.
7. Review hire purchase or lease documentation.
8. Record delivery, use, financing, VAT and the disposal plan.
9. Preserve invoices and the fixed-asset register.
10. Request a written computation and ask how the relief affects future disposals.

When to involve Britvex

Capital-allowance planning is most valuable before a business commits to equipment, a technology purchase, a commercial fit-out or a large vehicle decision. Britvex can examine the expenditure categories, bookkeeping evidence, company profit forecast and tax-return treatment, then identify where specialist valuation or legal advice may be required.

A new client can start through the Britvex portal or discuss UK tax planning. Existing clients can use the secure portal for equipment invoices, finance documents and supporting schedules. For an independent statutory reference, use GOV.UK Capital Allowances.