Capital Allowances for Sole Traders and Self-Employed UK 2026: Full Guide

Quick answer

Capital allowances are the tax mechanism that replaces accounting depreciation for self-employed people. When you buy a piece of equipment, a vehicle, or other business assets, you claim capital allowances to deduct that cost from your taxable profits. The system has several components: the Annual Investment Allowance (AIA) for immediate 100% deductions, Writing Down Allowance (WDA) for assets not covered by AIA, and special rules for cars tied to CO2 emissions. This guide covers all of them.

Why capital allowances exist

In accounting, the cost of a long-lived asset is spread over its useful life via depreciation. A £20,000 van might be depreciated over 5 years at £4,000 per year.

Tax law does not follow accounting depreciation. Instead, it has its own system — capital allowances — which dictates when and how much of an asset's cost you can deduct from taxable profits. The rules are standardised across all businesses, regardless of the accounting depreciation method used.

The practical result is that:

1. The total deduction over the asset's life is the same (you ultimately deduct the full cost)
2. The timing of those deductions differs — and timing matters because earlier deductions reduce your tax bill sooner

The four types of capital allowance for sole traders

1. Annual Investment Allowance (AIA)

The Annual Investment Allowance gives 100% relief in the year of purchase for qualifying plant and machinery. The annual limit is permanently set at £1,000,000.

For most sole traders, this limit is entirely sufficient — annual capital spending rarely approaches £1m. AIA is discussed in detail in our companion guide to AIA for sole traders, but the essentials are:

• Qualifying assets: plant and machinery (tools, computers, vans, machinery, office furniture, commercial vehicles)
• Excluded: cars (specifically excluded from AIA by statute)
• 100% deducted in the year of purchase or first use
• Both new and second-hand assets qualify

2. Writing Down Allowance (WDA)

Writing Down Allowance is the fallback for assets that either do not qualify for AIA or exceed the AIA limit. Instead of 100% deduction in year one, you deduct a fixed percentage each year on a reducing balance basis.

Assets are grouped into "pools":

Main pool — 18% WDA per year

• Most plant and machinery not covered by AIA
• Cars with CO2 emissions of 1–110g/km

Special rate pool — 6% WDA per year

• Integral features of buildings (electrical systems, heating, hot and cold water systems, lifts, external solar shading)
• Thermal insulation added to a building
• Long-life assets (expected useful life of 25 years or more)
• Cars with CO2 emissions above 110g/km

3. First Year Allowance (FYA)

First Year Allowances provide 100% deduction in year one for specific categories of qualifying asset. The most relevant for sole traders in 2026-27:

Zero-emission cars (0g/km CO2): New zero-emission cars — pure electric vehicles with no CO2 output — qualify for a 100% First Year Allowance. The full purchase price is deductible in the year of purchase or first use. This applies to cars purchased for business use by sole traders (the precise eligibility date for unincorporated businesses is from April 2021 onwards — check HMRC guidance for exact registration date requirements).

The 100% FYA for zero-emission cars is a significant incentive for self-employed people considering switching to an electric vehicle for business use. Combined with the private use restriction (see below), the calculation depends on the proportion of business mileage.

Note on historical FYAs: The Government previously offered 100% FYAs for energy-efficient equipment (the Green Technology List). This was largely abolished in April 2020. As of 2026, zero-emission vehicles are the primary remaining 100% FYA available to sole traders.

4. Structures and Buildings Allowance (SBA)

The Structures and Buildings Allowance applies to capital expenditure on constructing, converting, renovating, or purchasing qualifying commercial buildings and structures. The rate is 3% per year on a straight-line basis (not reducing balance).

SBA applies to:

• Commercial property construction or conversion costs
• Renovation or repair of commercial buildings that are capital in nature
• Legal and professional fees directly related to the construction

SBA does not apply to:

• Land (never qualifies for any capital allowance)
• Residential property
• Buildings already in use before the qualifying date

For most sole traders, SBA is only relevant if they own (rather than rent) commercial premises or have invested heavily in fit-out. It is a relatively slow allowance — at 3% per year, it takes over 33 years to fully write off a building cost. However, it is better than no allowance at all.

Capital allowances for cars: the detailed rules

Cars deserve special attention because they are excluded from AIA and have their own CO2-linked system. Understanding these rules is essential for any self-employed person who uses a vehicle.

Defining a "car" for tax purposes

Not every vehicle is a "car" for capital allowances purposes. The relevant test is whether the vehicle is:

• A mechanically propelled road vehicle
• Not a motorcycle
• Not a vehicle of a type not commonly used as a private vehicle and unsuitable for such use

In practice: vans are not cars for capital allowances purposes. A van (including transit vans, panel vans, and most pick-up trucks with a payload of at least 1 tonne) qualifies for AIA. A car does not.

HMRC applies a specific test to double-cab pick-up trucks, which have historically been in a grey area. Following case law and updated HMRC guidance (revised in 2024), double-cab pick-ups are now more likely to be treated as cars for tax purposes if they are primarily used as passenger vehicles. If you drive one, check the current HMRC guidance.

The CO2 pool system

Once a vehicle is classified as a car, it goes into a capital allowance pool based on CO2 emissions:

Private use restriction

This is one of the most important rules for self-employed people using a car for both business and personal journeys. The capital allowance is reduced by the proportion of private use.

Example: A sole trader buys a car for £25,000. CO2 emissions are 75g/km (main pool, 18% WDA). Business use is 70%, personal use is 30%.

• Year 1 WDA on full cost: £25,000 × 18% = £4,500
• Business use proportion: 70%
• Deductible amount: £4,500 × 70% = £3,150

The pool value carried forward is the full £25,000 × (1 - 18%) = £20,500 (the pool balance is not reduced by the private use restriction — only the deductible portion changes each year).

Practical implication: A car with significant personal use generates relatively small capital allowance deductions. Many sole traders find it simpler and often more tax-efficient to use the simplified mileage rate (45p per mile for the first 10,000 business miles, 25p per mile above that) rather than claiming actual costs plus capital allowances.

100% FYA for zero-emission cars: the numbers

A sole trader buys a new electric car for £45,000. Business use is 80%.

• FYA on full cost: £45,000 × 100% = £45,000
• Private use restriction (80% business): £45,000 × 80% = £36,000 deductible

At higher-rate income tax (40%), this saves £14,400 in the year of purchase. Even at basic rate (20%), the saving is £7,200. The tax incentive is substantial.

Pools explained: how the system works in practice

The main pool

The main pool accumulates most qualifying plant and machinery (other than AIA assets deducted immediately) and cars with CO2 of 1–110g/km. Each year, the pool balance is reduced by 18% WDA. Additions (new asset purchases) increase the pool. Disposals (proceeds from selling assets) reduce the pool.

Example of main pool over 3 years:

The pool "rolls over" from year to year. You never have to recalculate asset by asset — everything in the main pool is tracked as a single balance.

The special rate pool

The special rate pool works the same way but at 6% WDA per year. It contains high-CO2 cars, integral features, thermal insulation, and long-life assets.

The lower WDA rate means special rate pool assets take much longer to write off — a 6% reducing balance takes approximately 36 years to reach 10% of the original cost. This is one reason why integral features (such as commercial building electrical systems) are relatively slow capital allowances to use.

The small pools allowance

If either the main pool or special rate pool balance falls below £1,000, you can claim the entire remaining balance in that year — this is the "small pools allowance." It avoids years of tiny WDA claims on a near-zero pool.

When you sell or dispose of an asset

When you sell, scrap, give away, or otherwise dispose of a business asset, the proceeds are deducted from the relevant pool balance. If you sold an asset for more than the pool balance, this creates a balancing charge — a taxable addition that reflects the fact you have over-claimed allowances relative to the net cost.

Example: Your special rate pool balance is £3,000. You sell a car from that pool for £5,000.

• Pool balance: £3,000
• Sale proceeds deducted: £5,000
• Pool goes negative: -£2,000
• Balancing charge: £2,000 (added to your taxable profits)

This balancing charge reverses the over-deduction of allowances — in total, you have deducted more than the net cost of the assets.

Balancing allowances on cessation

When you permanently cease trading, the remaining balance in each pool is deducted as a balancing allowance in your final accounting period. This ensures that the full cost of all assets is eventually relieved against tax — no more drip-feed WDA payments after you have stopped trading.

Example: At cessation, main pool balance is £12,000. You sell all assets for a combined £8,000.

• Pool balance after disposals: £12,000 - £8,000 = £4,000
• Balancing allowance: £4,000 (deducted in your final tax year)

If you sell everything for more than the pool balance, a balancing charge arises instead (as described above).

The cessation rules mean it is important to track what you sell assets for when you close your business — underreporting sale proceeds saves nothing, but overreporting them creates an unnecessary tax charge.

Cash basis vs accruals: how the choice affects capital allowances

Since April 2023, the cash basis of accounting is the default for most self-employed individuals with annual turnover below the relevant threshold (check current HMRC guidance, as the threshold may be updated). Under the traditional accruals basis, capital allowances apply as described throughout this guide.

Under cash basis, the treatment of capital expenditure is simpler:

Equipment under cash basis

Capital expenditure on plant and machinery (other than cars) is automatically deductible in full in the year of payment under cash basis. There is no separate capital allowances calculation. Buy a £3,000 laptop, deduct £3,000 this year. The effect is identical to claiming AIA — but you do not need to track asset pools or calculate WDA.

Cars under cash basis

Cars are treated differently even under cash basis. You cannot simply deduct the purchase cost of a car. Instead, you either:

1. Use the simplified mileage rate — 45p per mile for the first 10,000 business miles per year, 25p per mile above that (for cars; different rates for motorcycles). No separate capital allowances. This is the easiest option and works well if you drive a moderate number of business miles.

2. Track actual costs — deduct actual fuel, insurance, servicing, and repairs, then claim capital allowances (WDA) on the car purchase cost, reduced for private use. This is more complex but may give a higher deduction if you have a low-emission car with high business use.

Important: Once you choose either method for a car, you must stick with it for the life of that car — you cannot switch between mileage rate and actual costs year by year.

When does cash basis not help?

Cash basis works well for equipment-heavy businesses with simple finances. It is less suitable if:

• You have significant business-use property (SBA does not interact simply with cash basis)
• You have large fluctuating profits where timing of deductions significantly affects your marginal rate
• You make very large capital purchases (over £500,000 in a year) — the accruals basis with AIA may give more flexibility

How to claim capital allowances on your SA103

Capital allowances for sole traders are reported on the SA103 (Self-employment) supplement of the Self Assessment tax return.

The key boxes:

Box 35 — Annual Investment Allowance Enter the total AIA-qualifying expenditure for the year. This reduces your adjusted profit.

Box 36 — Electric charge point allowance / 100% and other enhanced allowances For any First Year Allowances claimed (e.g., on a zero-emission car or electric vehicle charging equipment).

Box 37 — Structures and Buildings Allowance For qualifying construction and renovation expenditure at 3% per year.

Box 38 — Other capital allowances WDA, balancing allowances, or any other capital allowances not entered in the boxes above.

Box 39 — Total capital allowances The sum of all the above boxes. This total is deducted from your gross profit to arrive at your net profit for tax purposes.

If you use commercial tax software or an accountant, these figures are calculated automatically. If you self-file on paper or via HMRC's online return, you will need to calculate your pools manually.

Common mistakes to avoid

Claiming AIA on a car. Cars cannot claim AIA — this is a fundamental rule. If you enter a car purchase in the AIA box, HMRC may raise an enquiry and disallow the excess. Use the correct WDA pool instead.

Forgetting the private use restriction on a car. If your car is used for any personal journeys, you must reduce the WDA claim accordingly. HMRC routinely checks this in enquiries.

Not keeping records of asset costs and business use. Capital allowances claims must be supported by purchase invoices and evidence of business use (mileage logs for vehicles, usage records for mixed-use equipment).

Claiming SBA on residential property. SBA only applies to commercial premises. Residential property never qualifies for SBA, regardless of whether it is used partly for business.

Confusing depreciation with capital allowances. Accounting depreciation in your profit and loss account is not deductible for tax. Only capital allowances are deductible. If you have depreciation in your accounts, you add it back when calculating taxable profit, then deduct the capital allowances instead.

Not claiming AIA at all. Some sole traders, especially those who self-file without an accountant, fail to claim capital allowances on equipment purchases at all — treating them as non-deductible. This is a significant underclaim. All qualifying plant and machinery purchases should be reviewed for AIA eligibility.

Frequently asked questions

Do I need to keep an asset register?

There is no statutory requirement for a formal asset register, but you need to be able to support your capital allowance claims if HMRC enquires. Keep purchase invoices, note the date of purchase and the cost, and record the pool(s) into which each asset falls. A simple spreadsheet is sufficient for most sole traders.

What happens to pool balances if I take a year off and don't trade?

If you cease trading permanently, balancing allowances apply. If you temporarily stop trading (with intention to resume), the pools carry forward. No WDA is claimed in a year of non-trading — the balances simply sit unchanged until you resume.

Can I claim capital allowances on a home office?

Capital allowances are not typically available on the fabric of a residential property (walls, floors, roof). However, if you buy specific equipment exclusively for use in your home office — computers, desks, office chairs — these are qualifying plant and machinery and AIA can be claimed. You cannot claim SBA on the residential property itself. The simplified flat-rate home office deduction (£6/week for occasional use) is an alternative to tracking actual office costs.

I bought a van and used it privately for the first six months before using it for business — can I still claim AIA?

AIA is available from the date the asset is first used for business purposes (or the date of purchase if that is later). If you bought the van for personal use and only later introduced it into the business, the qualifying expenditure is the market value at the date of introduction to the business — not the original purchase price. This is an "introduced asset" rule. The deduction is based on the lower of original cost or market value at introduction.

Does my business structure affect which capital allowances I can claim?

Yes. Full Expensing (100% deduction with no cap) is available to limited companies only — it was introduced for companies from April 2023. Sole traders and partnerships do not have access to Full Expensing; AIA at £1,000,000 is their equivalent. The practical difference only matters if you spend more than £1,000,000 on qualifying assets in a year — above that threshold, companies can still deduct everything immediately, whereas sole traders must use WDA on the excess. For most sole traders, this distinction is academic.