What Is the AIA Allowance?
The Annual Investment Allowance (AIA) is a capital allowance that gives you 100% tax relief on qualifying plant and machinery costs, up to a set limit each year. For most businesses, including property companies and sole trader landlords, the current AIA limit is £1 million per annum [1].
This means you can deduct the full cost of qualifying assets from your taxable profits in the year you buy them, rather than spreading the relief over several years through writing down allowances.
The AIA is available to most businesses, but not to partnerships where one of the partners is a limited company [2]. If you are a sole trader landlord or a property company, you can typically claim it.
How Does the AIA Work for Property Investors?
For property investors, the AIA is most relevant when you own commercial property or furnished holiday lettings (though the FHL regime was abolished from April 2025). It also applies to plant and machinery you install in a rental property, such as heating systems, lifts, or security systems.
You can only claim AIA in the period you bought the item [1]. If your accounting period is shorter than 12 months, the AIA limit is proportionally reduced. For example, if your accounting period is 9 months, the AIA will be 9/12 x £1,000,000 = £750,000 [1].
If you buy something under a hire purchase contract, you can claim for all payments you will make under the contract once you start using the item [1]. This can be useful for landlords financing equipment over time.
What Qualifies for the AIA?
The AIA applies to most plant and machinery, but there are important exclusions. It does not cover cars, assets used for leasing, or assets with a life of more than 100 years [2].
For property investors, qualifying items typically include:
- Heating and ventilation systems
- Lifts and escalators
- Security systems (CCTV, alarms)
- Kitchen and bathroom fittings in commercial lets
- Solar panels and renewable energy installations
- Fixtures integral to a building (e.g., electrical systems, plumbing)
If an item qualifies for more than one capital allowance, you can choose which one to use [3]. This flexibility can help you optimise your tax position.
AIA Limit: Current and Historical Rates
The AIA limit has changed several times. Since 1 January 2019, the limit has been £1 million for both sole traders and limited companies [1]. This rate is confirmed until 31 March 2026 [2].
Historically, the limit was lower. For the tax year 2016/17, the total AIA that could be claimed was £200,000 [4]. The increase to £1 million was introduced to encourage business investment after the EU referendum, when business investment growth slowed [5].
From 1 April 2026, the AIA limit is expected to revert to £200,000, though this has not been confirmed in legislation as of early 2026. You should plan your capital expenditure accordingly.
AIA vs Full Expensing: What's the Difference?
Full expensing was introduced from 1 April 2023 for limited companies, allowing 100% relief on qualifying plant and machinery with no cap [3]. This is similar to the AIA but is only available to companies, not sole traders or partnerships.
The super-deduction (130% relief) and 50% special rate first-year allowance applied to plant and machinery bought from 1 April 2021 to 31 March 2023 [3]. These have now ended.
For most property investors operating as sole traders or partnerships, the AIA remains the primary route for claiming 100% relief on plant and machinery costs. If you operate through a limited company, full expensing may be more generous for large investments above the AIA cap.
How to Claim the AIA
You claim the AIA through your tax return or company tax return. For sole traders, include the claim in your self-assessment tax return. For limited companies, claim it in your company tax return (CT600).
You need to identify the qualifying expenditure and calculate the amount of AIA you want to claim. Any expenditure above the AIA limit enters the main pool or special rate pool and attracts writing down allowances instead [2].
Writing down allowances can be claimed if plant and machinery does not qualify for another allowance, or if there is value remaining after claiming the maximum amount of another allowance [3].
If you are unsure about what qualifies, it is worth speaking to a specialist property accountant who can review your capital expenditure and ensure you claim everything you are entitled to.
Special Rules for Property Companies
If you own property through a limited company, there are additional rules to be aware of. If 2 or more limited companies are controlled by the same person, they only get one AIA between them [1]. This means you cannot claim the full £1 million limit for each company in a group.
For companies, the AIA limit applies to the accounting period. If your company has a 12-month period, you get the full £1 million. If the period is shorter, it is proportionally reduced.
If you are considering incorporating your property portfolio, the AIA can be a significant benefit. A limited company can claim AIA on qualifying plant and machinery, which can reduce corporation tax. For more on this, see our guide on incorporation for property investors.
AIA and Commercial Property
For investors in commercial property, the AIA is particularly valuable. You can claim on fixtures and fittings you install in a commercial building, such as heating, lighting, and ventilation systems.
If you buy a commercial property that already has qualifying plant and machinery, you may be able to claim capital allowances on the purchase price. This requires a capital allowances valuation, which should be done within two years of purchase.
Section 24 does not apply to commercial property, so mortgage interest remains fully deductible against rental income. This makes commercial property more tax-efficient for higher-rate taxpayers. For a full breakdown of allowable deductions, see our complete list of landlord tax deductions.
AIA and Residential Property
For standard residential buy-to-let properties, the AIA is less commonly used. This is because most residential landlords do not install significant plant and machinery in their properties. However, if you install a new heating system, solar panels, or a security system, these may qualify.
Note that the AIA does not apply to the cost of the building itself or to land. It only applies to plant and machinery. If you are refurbishing a property, the distinction between repairs (revenue) and improvements (capital) is important. Repairs are deductible immediately, while improvements may qualify for capital allowances.
For a comprehensive overview of how property income is taxed, see our rental income tax guide.
Planning for the AIA Limit Change
With the AIA limit expected to drop from £1 million to £200,000 from 1 April 2026, property investors should plan their capital expenditure carefully. If you are considering significant plant and machinery investments, it may be beneficial to bring them forward to before the change.
Business investment accounts for around 10% of GDP in the UK [5], and the government has used the AIA to encourage investment. The higher limit has been extended several times, but the current legislation sets the end date at 31 March 2026 [2].
If you are a property developer or investor with large capital projects, the reduction in the AIA limit could significantly affect your tax position. You may need to consider full expensing (if you are a company) or writing down allowances for expenditure above the new limit.
Common Mistakes to Avoid
One common mistake is claiming AIA on assets that do not qualify, such as cars or assets used for leasing. Another is forgetting to claim in the correct period, you can only claim AIA in the period you bought the item [1].
Some landlords also miss the opportunity to claim AIA on hire purchase items. If you buy something under a hire purchase contract, you can claim for all payments you will make under the contract once you start using the item [1].
Finally, if you have multiple property companies under common control, remember that they share one AIA limit. Trying to claim the full £1 million for each company would be incorrect.
How a Property Accountant Can Help
Claiming the AIA correctly requires a good understanding of capital allowances rules and how they apply to property. A specialist property accountant can review your capital expenditure, identify qualifying items, and ensure your claim is maximised.
They can also help with the distinction between repairs and improvements, which is a common area of confusion for landlords. For more on what a property accountant does, see our guide on what a property accountant does.
If you are considering incorporating your portfolio, an accountant can advise on the tax implications and help you structure your affairs to maximise reliefs like the AIA. For more on the costs involved, see our guide on property accountant costs.
Final Thoughts
The AIA allowance is a valuable tax relief for property investors who invest in plant and machinery. With a current limit of £1 million, it allows you to deduct the full cost of qualifying assets in the year of purchase, reducing your taxable profits and tax bill.
However, the rules are detailed, and the limit is due to change from April 2026. If you are planning significant capital expenditure, it is worth getting professional advice to ensure you claim correctly and optimise your tax position.
For personalised advice on the AIA and other capital allowances, contact our team of specialist property accountants. We help landlords and property investors across the UK, from London to Manchester to Edinburgh.
Sources
- gov.uk: Claim capital allowances: Annual investment allowance - GOV.UK
- icaew.com: A lowdown on full expensing for SMEs - ICAEW.com
- aka.hmrc.gov.uk: Claim capital allowances: Overview - GOV.UK
- nature.com: For specialist tax planning advice | British Dental Journal - Nature
- bankofengland.co.uk: Influences on investment by UK businesses: evidence from the...