Annual Investment Allowance: Claiming Capital Allowances (UK)

What the Annual Investment Allowance actually does

When your business buys equipment, HMRC does not normally let you deduct the full cost against profit in one go — ordinarily that cost would be spread over several years through capital allowances. The Annual Investment Allowance (AIA) is the exception: it lets most UK businesses deduct 100% of qualifying capital expenditure against their taxable profit in the same accounting period the purchase was made, up to an annual limit of £1 million.

The £1 million limit has applied since April 2019 and was made a permanent feature of the capital allowances regime from April 2023, rather than a temporary uplift that periodically reverts to a lower figure as it once did. For the overwhelming majority of sole traders and small companies, spending nowhere near £1 million a year on equipment, the AIA simply means: buy the equipment, claim the full cost against profit that year.

What qualifies for AIA

AIA applies to most plant and machinery bought for use in the business, including:

• Computers, laptops, and office IT equipment
• Tools and machinery used in a trade
• Vans, lorries, and other commercial vehicles (but not cars — see below)
• Office furniture and fixtures
• Certain integral features of a building (electrical systems, heating, and similar), subject to specific rules

The expenditure has to be for a qualifying business purpose. Where an asset is used partly for personal purposes (common for sole traders — a laptop or van used privately as well as for the business), only the business-use proportion of the cost can be claimed.

What does not qualify

A few categories are specifically excluded from AIA, even though they might otherwise look like plant and machinery:

• Cars are never eligible for AIA — they are dealt with under separate capital allowance rules (main rate or special rate pool, with the rate depending on the car's CO2 emissions), typically written down more slowly at 18% or 6% a year on a reducing balance basis
• Assets bought for leasing out to someone else (with some exceptions)
• Anything bought in the final accounting period before a business ceases trading
• Land and buildings themselves (structures and buildings relief is a separate, much slower relief)

Full expensing for limited companies

Limited companies also have access to full expensing, introduced alongside the AIA changes from April 2023 and made a permanent feature at a later fiscal event. Full expensing gives a 100% first-year deduction on qualifying new and unused main-rate plant and machinery, with no cap on the amount — unlike AIA, which is capped at £1 million. Full expensing is only available to companies within the charge to Corporation Tax, not to sole traders or partnerships, and the detailed qualifying conditions are worth checking with your accountant if a large single purchase is involved.

Capital allowances rules are detailed and change periodically at fiscal events — confirm current thresholds and qualifying conditions on gov.uk, or with your accountant, before relying on a specific figure for a large purchase.

How to make the most of your AIA

A few practical points worth knowing:

• Timing matters. The AIA applies in the accounting period the expenditure is incurred, which is generally when the legal obligation to pay arises — not necessarily when cash leaves the bank. If you are close to a year end and planning a large purchase, discuss the timing with your bookkeeper or accountant, since it can affect which year's profit the deduction falls into.
• Hire purchase still qualifies. Equipment bought under a hire purchase agreement generally qualifies for AIA in the period the asset is brought into use, even though payments are spread over time — this is different from a straightforward rental or operating lease, where the business never owns the asset.
• Keep the paperwork. Invoices, purchase agreements, and evidence of business use should be kept in case HMRC queries the claim, particularly for higher-value or mixed-use assets.
• Do not assume every purchase automatically qualifies. If in doubt about whether a specific item counts as plant and machinery, ask before assuming — cars, certain buildings-related costs, and leased-out assets are the most common areas where business owners claim AIA incorrectly.

Recording capital purchases correctly

In Xero or QuickBooks, capital purchases should be coded to a fixed asset account rather than run straight through as a general expense — this keeps your balance sheet accurate and gives your accountant a clean starting point for capital allowances at year end. As mentioned in our guide to year-end accounts for sole traders, equipment purchased during the year needs to be flagged clearly rather than buried inside a broader expense category, since misclassifying it can mean the AIA claim is missed entirely.

If you are unsure whether a purchase should be expensed or capitalised, that is exactly the kind of question worth raising with your bookkeeper as it happens, rather than at year end when the option to fix the coding easily has often passed.