Buying a car for business use should be one of the simpler tax decisions a small business owner makes. In practice, it is one of the trickiest. The tax relief you can claim depends on four separate variables: who owns the car (you personally as a sole trader, or your company), how you finance it (cash, hire purchase, or lease), how old it is (new and unused, or second-hand), and what comes out of the tailpipe (zero, low, or higher emissions). Get any one of these wrong and the relief can range from a 100% deduction in year one to a 6% writing-down allowance that takes nearly two decades to fully recover.

This guide pulls all four threads together. By the end you should know how the 2026 rules apply to your situation, where the lease rental restriction bites, and why a used Tesla and a new Tesla are treated very differently for tax. If you would like specific advice on a purchase you are weighing up, FSL Accountancy reviews these decisions for clients across the UK every week.

Why Cars Are Treated Differently to Other Business Assets

For most plant and machinery, businesses can claim either the Annual Investment Allowance (AIA) of up to £1 million in the year of purchase, or — for companies from 1 April 2023 — full expensing on new and unused qualifying assets. From 1 January 2026 a further 40% First-Year Allowance arrived for businesses that cannot use full expensing. None of these generous reliefs apply to cars.

A car for capital allowances purposes is a mechanically propelled road vehicle that is not a goods vehicle, not commonly used as a public-service vehicle, and not unsuitable for use as a private vehicle. Vans, double-cab pickups (subject to specific rules), lorries and many specialist vehicles fall outside this definition and get the more generous AIA or full-expensing treatment. A standard saloon, hatchback, estate or SUV almost always counts as a car and is locked into the slower car-specific regime.

That regime gives you three possible rates depending on the car’s CO₂ emissions and whether it is new or used.

The Three Capital Allowance Routes for Cars in 2026

100% First-Year Allowance: New, Unused, Zero-Emission Cars

If you buy a brand-new, never-previously-used, zero-emission car (a pure-electric or hydrogen fuel-cell vehicle with 0 g/km CO₂), you can deduct the entire purchase price from your taxable profits in the year of purchase. This is the 100% First-Year Allowance under section 45D of the Capital Allowances Act 2001. Following the 2025 Budget, the relief has been extended to 31 March 2027 for corporation tax purposes and 5 April 2027 for income tax purposes. After that date, in the absence of a further extension, zero-emission cars will drop back into the main pool and receive only writing-down allowances.

The conditions are strict. The car must be new and unused — ex-demonstrator or pre-registered stock can fail this test. It must be owned outright by the business (cash or hire purchase). It must be in business use. And the expenditure must fall within the qualifying period.

[H3] Main Pool: 18% Falling to 14%

Cars with CO₂ emissions of 50 g/km or less that do not qualify for the FYA — for example, a used electric car or any plug-in hybrid with low CO₂ emissions — enter the main rate pool. The same applies to new cars between 1 and 50 g/km, which lost their First-Year Allowance status from April 2021.

The main pool currently gives an 18% writing-down allowance per year on a reducing-balance basis. From 1 April 2026 (corporation tax) and 6 April 2026 (income tax), this rate drops to 14%. For accounting periods that straddle the change-of-rate date, the rate is apportioned on a daily basis. The slower rate makes timing of purchases more important than it has been for years — a car bought in February 2026 by an income tax business gets the full 18% for the year, while one bought in May gets a blended rate.

Special Rate Pool: 6%

Any car with CO₂ emissions above 50 g/km goes into the special rate pool, regardless of whether it is new or used, regardless of whether it is petrol, diesel or hybrid. The writing-down allowance is just 6% per year on a reducing-balance basis. On a £30,000 SUV, that gives £1,800 of relief in year one — and the unrelieved cost can sit on the books for the best part of two decades before it is fully written down.

This is the single biggest reason higher-emission cars are tax-inefficient compared to electric alternatives. A £30,000 new EV bought before April 2027 gives £30,000 of immediate relief; the same money spent on a high-emission SUV gives just £1,800 in year one. At the small profits corporation tax rate of 19%, that is a year-one cash tax difference of about £5,358.

Here is how the rates compare side-by-side:

New Versus Second-Hand: Why Used Electric Cars Are Penalised

The most counter-intuitive rule in the car capital allowances regime is the new-and-unused condition for the 100% FYA on electric vehicles. The relief was designed to drive demand for new zero-emission cars and stimulate the manufacturer supply chain. It does nothing for the used market.

A used Tesla Model 3 purchased outright for £25,000 enters the main pool, gives a £4,500 deduction in year one at the current 18% rate (falling to £3,500 at the new 14% rate from April 2026), and recovers the balance over many subsequent years. A brand-new Tesla Model 3 purchased outright for the same money would give a £25,000 deduction in year one. The car is identical from a road-use perspective. The tax relief is dramatically different.

For higher-mileage business users, the case for buying new before April 2027 is therefore stronger than the used-EV market discount might initially suggest. For lower-mileage users, the second-hand discount may still win on a total-cost-of-ownership basis once depreciation is factored in. There is no one-size answer — the right call depends on price, mileage, tax rate, and how soon profits will absorb the relief.

Ownership Structure: Sole Trader Versus Limited Company

Capital allowances rules are broadly the same for both, but the way they interact with private use is very different — and that single difference often determines which structure should buy the car.

Sole Trader and Partnership: The Private Use Restriction

If you are self-employed and the car will also be used privately (any commuting from home to a permanent workplace counts), you can only claim the business-use proportion of the capital allowances. A car with 70% business use and 30% private use gives 70% of the otherwise-available allowance.

HMRC also requires the car to be held in a separate single-asset pool rather than being added to the main pool. This sounds bureaucratic but it has real consequences. When the car is sold, the difference between the sale proceeds and the unrelieved tax cost gives rise to either a balancing allowance (further relief) or a balancing charge (taxable claw-back). With a single-asset pool you get to that calculation cleanly. With a car in the main pool, the disposal proceeds are simply netted off the pool, often masking the real tax outcome on that specific vehicle.

The simplified mileage method offers an alternative for sole traders and is examined later in this guide.

Limited Company: Full Capital Allowances, but a Benefit in Kind

A limited company that owns a car claims 100% of the capital allowances regardless of how the director uses the vehicle. The trade-off is that any private use creates a benefit-in-kind charge on the driver. For most cars, the BIK is calculated as the manufacturer’s list price multiplied by an appropriate percentage based on CO₂ emissions.

For zero-emission electric vehicles, the BIK percentage has been very low for several years. It is rising on a published schedule — 3% in 2025/26, 4% in 2026/27, 5% in 2027/28, then 7% in 2028/29 and 9% in 2029/30 — but remains far below the 25% to 37% bands that apply to most petrol and diesel cars. Combined with the 100% FYA on the purchase and the absence of fuel benefit (electricity provided by the employer for business or private mileage is not currently a taxable benefit), an electric company car remains one of the most tax-efficient remuneration tools available to a small limited company.

For higher-emission cars the calculation flips. A £45,000 petrol SUV with 180 g/km CO₂ emissions generates a BIK around £16,650 a year, costing a higher-rate director roughly £6,660 in personal tax and the company around £2,300 in Class 1A National Insurance — and that is on top of the slow 6% capital allowances. For most owner-managed limited companies, putting a high-emission car through the company is now a money-losing decision.

How You Pay for the Car: Hire Purchase, Lease, or Cash

Tax law looks past the marketing label of a finance product and asks a single question: who is the economic owner of the asset? The answer determines whether you are buying the car or renting it — and that drives the tax treatment.

Hire Purchase: Treated as an Outright Purchase from Day One

Under a typical hire purchase agreement, the finance company owns the car legally until the final option-to-purchase payment, but the business takes economic ownership immediately. For capital allowances, HMRC treats the full cash price (excluding finance charges) as qualifying expenditure on the day the car is brought into use. A new electric car bought on HP can therefore qualify for the full 100% FYA in year one, even though the business has only paid a deposit and one month’s instalment by year end.

The interest element of the HP payments is deducted separately, through the profit and loss account, as a financing cost. The capital element does not appear as a P&L expense at all — it is recovered through the capital allowances regime instead. Mixing the two up is one of the most common errors we see on draft small-company accounts.

Operating Lease and Contract Hire: No Capital Allowances at All

Under contract hire or any other operating lease, the leasing company remains the owner of the car throughout. The business is simply paying for the right to use it. There is no qualifying expenditure on the part of the lessee and therefore no capital allowances claim. Instead, the monthly rentals are deducted directly from taxable profits as a business expense — subject to the 15% lease rental restriction described below.

The 15% Lease Rental Restriction

Where a business leases a car with CO₂ emissions above 50 g/km, 15% of the lease rentals are disallowed for tax. Only 85% of the cost can be deducted from taxable profits. The rule is identical for sole traders, partnerships and companies, and it applies to operating leases and finance leases alike. Pure electric cars and any car with emissions of 50 g/km or below escape the restriction entirely and get a 100% deduction.

Where a maintenance element is bundled into the rental, the disallowance applies only to the lease portion provided the contract identifies the maintenance charge separately. If the contract simply shows a single all-inclusive figure, HMRC will apply the disallowance to the whole rental.

Finance Lease: The Awkward Middle Ground

A finance lease sits between an operating lease and an HP agreement. The business does not legally own the car but takes substantially all the risks and rewards of ownership. Under FRS 102 and IFRS 16, the asset usually sits on the balance sheet with a corresponding liability. For tax purposes, however, most finance leases of cars are treated like operating leases: the depreciation through the P&L is replaced by the rental expense, subject to the 15% restriction for high-emission cars, with no capital allowances claim. There are limited exceptions where the lease is treated more like an HP arrangement, but these are rare for small-business cars and need professional review.

Worked Example: Same Car, Four Different Outcomes

Take a £35,000 saloon car bought for a small limited company in May 2026, with 100% business use and a CO₂ figure that depends on the variant chosen.

• New, unused, electric (0 g/km), purchased outright or on HP: £35,000 of relief in year one under the 100% FYA. At the small profits corporation tax rate of 19%, year-one tax saving is £6,650.
• Used electric (0 g/km), purchased outright or on HP: Main pool, 14% WDA. Year-one relief of £4,900, ongoing relief of around £4,200 in year two, falling thereafter.
• New petrol, 145 g/km CO₂, purchased outright or on HP: Special rate pool, 6% WDA. Year-one relief of £2,100. Recovery continues at 6% of the reducing balance for many years.
• Same petrol car on a 3-year contract hire at £550 per month: Annual rentals of £6,600, of which 85% (£5,610) is deductible. The 15% restriction adds back £990 to taxable profits each year.

The same physical car can produce a year-one tax deduction anywhere between £2,100 and £35,000 depending on the choices made. This is why advice before purchase — not after — is worth far more than it costs.

Disposal: What Happens When You Sell or Trade In

Cars in the Main Pool or Special Rate Pool

When you sell a car that sits in the main or special rate pool, the sale proceeds (capped at original cost) are deducted from the pool’s tax written-down value. If the pool stays positive, future writing-down allowances simply reduce. If the pool goes negative, the excess becomes a balancing charge — additional taxable profit in the year of disposal. Where the pool contains other assets, gains and losses on individual cars are effectively blended.

Single-Asset Pool Disposals (Sole Traders with Private Use)

For sole traders, where the car has been held in a single-asset pool due to private use, the disposal calculation is direct. The sale proceeds are compared to the tax written-down value. The difference is a balancing allowance (deductible) if the proceeds are lower, or a balancing charge (taxable) if higher. Either way, the private-use proportion is applied so that only the business element ends up in the tax computation.

Balancing Charges on 100% FYA Cars

This is the trap most often missed on new electric cars. If you claimed 100% FYA on a new EV and later sell it, the car has zero tax written-down value, so all of the sale proceeds reduce the pool the car sits in. For a limited company, this means the proceeds are deducted from the main pool: if the pool has enough value in it from other assets to absorb the deduction, no immediate tax charge arises — but future capital allowances on the remaining pool will be lower. If the pool goes negative, the excess crystallises as a balancing charge taxable in that year. For a sole trader’s car held in a single-asset pool, the position is starker: the disposal will almost always create a balancing charge equal to the proceeds (adjusted for private use).

Either way, a significant portion of the original tax relief is effectively clawed back. Build the eventual exit into your modelling at the point of purchase — a car you plan to sell after two years gives a very different effective tax saving from one you plan to keep for seven.

The Simplified Mileage Alternative for Sole Traders

Sole traders and partnerships of individuals (not partnerships including a company) can choose to use the simplified mileage method instead of claiming capital allowances and actual running costs. From 6 April 2026 the rates increased for the first time since 2011: 55p per business mile for the first 10,000 miles in the tax year (previously 45p), and 25p per mile thereafter. Motorbikes remain at 24p per mile and bicycles at 20p per mile.

Once you choose simplified mileage for a particular car, you must stick with it for as long as you use that car for business. You cannot switch back to capital allowances mid-way through the car’s life. Mileage is generally the right call for cars under £15,000 with moderate business use and low running costs. Capital allowances plus actual costs tends to win for higher-value cars, electric cars qualifying for the 100% FYA, and high-mileage commercial users. The 10p uplift in 2026 has improved the mileage method’s relative attractiveness, particularly at the 10,000-mile threshold.

Limited companies cannot use simplified mileage for company-owned cars. They can pay tax-free mileage allowances to employees and directors who use their own personal cars for business, at the same 55p / 25p rates — but that is a different mechanism with different consequences.

Practical Planning Pointers for 2026 and 2027

• Use the 100% FYA window. If a new electric car is on your shopping list, the relief expires on 31 March 2027 (CT) or 5 April 2027 (IT) in the absence of a further extension. Locking in 100% relief while it is available is straightforward planning.
• Time the main pool rate change. The reduction from 18% to 14% in April 2026 will pull forward the tax cash flow benefit for purchases made before the change-of-rate date. For cars sitting in the main pool, an earlier purchase gives a marginally faster recovery.
• Beware the used-EV gap. Used electric cars are tax-disadvantaged compared with new ones. Always model both before committing.
• Match financing to expected ownership length. If you genuinely intend to keep the car long-term, HP plus capital allowances is usually best. If you change cars every three years, contract hire avoids both the disposal balancing charge and the risk of poor residual value.
• Consider VAT separately. Input VAT on car purchases is generally blocked unless the car is exclusively used for business with no private use whatsoever (a very high bar). For leases, 50% of the VAT on the rental is recoverable. VAT and capital allowances should be considered together, not in isolation.
• Factor in benefits in kind. A company-owned car that delivers full corporation tax relief but generates a £6,000+ annual BIK is rarely a net win. Run the combined calculation before signing.

Common Mistakes We See Each Year

• Claiming AIA on a car. The AIA does not apply to cars, full stop. We still see this error on draft tax computations every season.
• Claiming the 100% FYA on a used electric car. The new-and-unused condition is binary — there is no partial relief for a one-month-old pre-registered car.
• Treating HP payments as fully deductible. Only the interest is deductible through the P&L; the capital element is recovered through capital allowances.
• Forgetting the 15% lease rental restriction on contract hire for petrol or diesel cars.
• Mixing personal use into a company-owned car without reporting a benefit in kind. HMRC pulls this out of routine PAYE compliance reviews regularly.
• Failing to use a single-asset pool for a sole trader’s part-private car, so balancing allowances and charges are never crystallised.

When to Get Specialist Advice

Car capital allowances look formulaic on paper. In practice, every variable interacts with every other one — CO₂, ownership structure, finance method, business-use percentage, BIK exposure, expected disposal date, VAT, and the impact on the wider tax computation. The right answer for one business is often the wrong answer for the next.

At FSL Accountancy, we work with sole traders, partnerships and limited companies across the UK to plan vehicle purchases, lease decisions and disposal timing so that the maximum tax relief is actually claimed and the BIK position is fully understood before the keys change hands. Whether you are choosing between buying and leasing your next car, deciding whether to put it through the company or pay mileage personally, or considering a switch to electric, get in touch and we will model the options for your specific situation.

Final Thoughts

The capital allowances regime for cars is one of those areas where small details have very large consequences. A new electric car and a used electric car can give relief that differs by more than £25,000 in year one. A petrol SUV bought on HP and the same car taken on contract hire can move the deductible expense by a third. A sole trader with 60% business use and a director with 100% company-owned use can extract very different amounts of value from the same purchase.

None of this is intended to overwhelm the decision. It is intended to highlight that the choice of car, financing method and ownership structure is a tax decision as much as a transport decision — and one worth a short conversation with your accountant before, not after, the contract is signed.