What Is the Annual Investment Allowance?
The annual investment allowance (AIA) is a capital allowance that lets you claim a full tax deduction on qualifying plant and machinery costs in the year you buy them. For most businesses, including property rental businesses, the AIA is set at £1 million per year [1].
This means if you spend £50,000 on a new boiler system for a block of flats you let out, you can deduct the full £50,000 from your taxable profits in that accounting period, rather than spreading the deduction over several years through writing-down allowances.
The AIA is particularly valuable for landlords who own property through a limited company, because corporation tax rates (19% to 25%) mean the tax saving is substantial. For individual landlords, the allowance reduces your income tax bill at your marginal rate.
Who Can Claim the Annual Investment Allowance?
The AIA is available to most businesses that pay UK tax on their profits. This includes:
- Limited companies that own buy-to-let properties
- Sole traders and partnerships running a property rental business
- Property developers and traders
However, there is an important restriction for sole traders and partnerships. If you use the cash basis of accounting for your rental income, you can only claim capital allowances on business cars [2]. Most residential landlords with small portfolios use the cash basis, so this rule catches many people out.
If you use accruals accounting (the traditional method), you can claim AIA on a wider range of plant and machinery. Our guide on landlord tax deductions explains the difference between cash and accruals basis in more detail.
What Qualifies for the Annual Investment Allowance?
To qualify for AIA, the item must be "plant and machinery" for tax purposes. This includes:
- Fixtures in a rental property, such as boilers, heating systems, lifts, and air conditioning
- Kitchen and bathroom fittings in furnished properties
- Furniture, white goods, and furnishings in furnished lettings
- Solar panels and other energy-saving equipment
- Office equipment used to manage your property portfolio
Land does not qualify, nor do buildings themselves. You cannot claim AIA on the cost of buying a property, only on the plant and machinery within it. If you buy a property that already contains qualifying fixtures, you may need a capital allowances valuation to apportion the purchase price.
For a full breakdown of what counts as plant and machinery in a rental context, see our property accountant services page, which covers capital allowances planning.
How Much Can You Claim?
The AIA is £1 million per 12-month accounting period [1]. This is a generous allowance that covers most landlords' capital expenditure in a typical year.
If your accounting period is shorter than 12 months, the allowance is proportionally reduced. For example, if your company's first accounting period is 9 months long, the AIA cap is 9/12 × £1,000,000 = £750,000 [1].
If your accounting period is longer than 12 months, you get the allowance for each 12-month period within it. So a 15-month period would give you £1 million for the first 12 months and £250,000 for the remaining 3 months (3/12 × £1,000,000).
The £1 million cap has been in place since 1 January 2019 [3]. Before that, the AIA was temporarily set at £1 million from January 2019, having been £200,000 for the 2018/19 tax year.
When Can You Claim the AIA?
You can only claim AIA in the accounting period in which you bought the item [1]. The date you bought it depends on the payment terms:
- If payment is due within less than 4 months of signing the contract, the date of purchase is when you signed the contract
- If payment is due more than 4 months later, the date of purchase is when payment becomes due [1]
If you buy something under a hire purchase contract, you can claim AIA when you start using the item, for all payments you will make under the contract [1]. This is useful for landlords who finance equipment purchases through HP.
There is a special rule if your business closes. You cannot claim AIA for items bought in the final accounting period [1]. This typically applies when a company is wound up or a sole trader retires.
How Does the AIA Interact with Other Capital Allowances?
The AIA is just one type of capital allowance. Others include:
- Writing-down allowances, for plant and machinery that does not qualify for AIA, or if you exceed the £1 million cap
- Full expensing, available to companies from 1 April 2023, allowing a 100% deduction on qualifying main-rate plant and machinery [2]
- 50% first-year allowance, for special-rate assets (e.g. integral features, long-life assets) bought by companies from 1 April 2023 [2]
- 40% first-year allowance, for qualifying plant and machinery purchased after 1 January 2026 [2]
The super-deduction (130% allowance) and 50% special rate first-year allowance were available from 1 April 2021 to 31 March 2023 [2]. These have now been replaced by full expensing and the 50% first-year allowance.
For most landlords, the AIA is the most straightforward option. If you spend more than £1 million in a year, the excess falls into the main pool and attracts writing-down allowances at 18% per year (or 6% for special-rate assets).
Annual Investment Allowance for Limited Companies vs Sole Traders
The AIA rules are broadly the same for all business structures, but there are practical differences:
- Limited companies, Can claim AIA on a wider range of assets. Corporation tax relief at 19% to 25% makes the allowance highly valuable. Companies can also access full expensing from April 2023.
- Sole traders and partnerships, If using cash basis, restricted to claiming capital allowances only on business cars [2]. If using accruals basis, the full AIA is available.
Many landlords choose to incorporate their portfolio into a limited company to access better tax reliefs, including full capital allowances. Our incorporation guide explains the process and tax implications.
Common Mistakes Landlords Make with the AIA
Here are the most frequent errors we see:
- Claiming on buildings, You cannot claim AIA on the cost of the property itself, only on plant and machinery within it
- Missing the cash basis restriction, Sole traders using cash basis cannot claim AIA on most items, only on cars
- Not apportioning purchase prices, When buying a property with fixtures, you need a capital allowances valuation to separate the building cost from the plant and machinery
- Claiming in the wrong period, The AIA must be claimed in the period you bought the item, not when you paid for it (if payment is deferred)
- Forgetting about hire purchase, You can claim AIA on HP items when you start using them, even though you have not yet paid the full amount
If you are unsure about any of these points, it is worth speaking to a specialist property accountant. Our services page explains how we help landlords with capital allowances planning.
How to Claim the Annual Investment Allowance
Claiming the AIA is straightforward:
- Identify all qualifying plant and machinery expenditure in the accounting period
- Calculate the total cost (use market value if you owned the item before starting to use it in your business, or if it was a gift) [2]
- Include the AIA claim in your tax return (company tax return for limited companies, self-assessment for sole traders and partnerships)
- Ensure the claim does not exceed the £1 million cap for the period
For limited companies, the claim is made on the CT600 corporation tax return. For sole traders and partnerships, it goes on the self-assessment tax return. If you use accounting software, most packages have a capital allowances section where you can enter the expenditure.
If you are approaching the Making Tax Digital deadline for landlords (April 2026 for those with gross income over £50,000), ensure your digital records capture capital expenditure correctly so you can claim the AIA without errors.
Planning Your Capital Expenditure to Maximise the AIA
Because the AIA is a 100% deduction in the year of purchase, timing your capital expenditure can significantly reduce your tax bill. If you know you will have a high-profit year, consider bringing forward planned purchases of plant and machinery to that year.
For example, if you are a higher-rate taxpayer with a limited company paying 25% corporation tax, spending £100,000 on qualifying plant and machinery saves you £25,000 in tax. If you delay the purchase to a lower-profit year, the saving may be less.
However, do not let tax drive poor business decisions. The AIA is generous enough that most landlords can claim it in the year they make the purchase regardless of profit levels.
For landlords with large portfolios, the £1 million cap may be reached in a single year. In that case, consider spreading large capital projects across two accounting periods to maximise the allowance.
What Happens If You Sell an Asset on Which You Claimed AIA?
When you sell an asset on which you claimed AIA, the proceeds are deducted from the relevant capital allowances pool. If the pool balance becomes negative, the excess is added to your taxable profits as a balancing charge.
This means the tax relief you received upfront is effectively clawed back when you dispose of the asset. However, because the AIA gives you 100% relief immediately, the timing advantage is still valuable, you get the tax saving now and pay tax later, which is better for cash flow.
If you sell the asset for less than its tax written-down value, you may get a balancing allowance, which is an additional deduction.
Frequently Asked Questions
Sources
- gov.uk: Claim capital allowances: Annual investment allowance - GOV.UK
- aka.hmrc.gov.uk: Claim capital allowances: Overview - GOV.UK
- icaew.com: Capital allowances | Tax - ICAEW.com