Annual Investment Allowance 2026: £1m Limit and Timing Your Capital Spend

The Annual Investment Allowance is one of the most powerful tools in a business owner's tax planning toolkit, giving immediate 100% tax relief on up to £1 million of capital expenditure per year. But the timing of purchases relative to your accounting year-end can dramatically affect how much relief you get -- and when.

What the Annual Investment Allowance Covers

The AIA gives 100% first-year relief on qualifying plant and machinery expenditure. This is the most straightforward capital allowance: spend money on a qualifying asset, claim 100% of the cost against taxable profits in the same period, and reduce your tax bill immediately.

Qualifying assets include virtually all business equipment and machinery:

• Manufacturing machinery and tools
• IT equipment, servers and software (where treated as plant)
• Fixtures and fittings in commercial property
• Integral features: electrical systems, heating, ventilation, air conditioning, water systems, lifts
• Vans, lorries, forklift trucks and other commercial vehicles (not cars)
• Agricultural equipment
• Office furniture and equipment

Assets that do not qualify for AIA:

• Cars: Defined by HMRC as vehicles not suitable for a substantial load, designed or modified for private use. These go into the capital allowance pools.
• Land: Capital land acquisition has no capital allowances treatment.
• Buildings and structures: The separate Structures and Buildings Allowance at 3% per year applies.
• Assets acquired for leasing: Certain leasing assets have restrictions.

Timing Purchases to Maximise AIA

The AIA is based on the accounting period, not the calendar year. A business with a 31 March year-end has £1m of AIA for the year 1 April 2025 to 31 March 2026, and another £1m for 1 April 2026 to 31 March 2027. Purchasing close to the year-end and then again shortly after creates an opportunity to claim substantial relief over a compressed calendar period.

Example: A business with a 31 March year-end plans to spend £1.8m on new machinery. If it spends £900,000 in March 2027 (using almost all of that year's AIA) and £900,000 in April 2027 (using almost all of the next year's AIA), it gets £1.8m of AIA relief over approximately two months of actual calendar time.

If instead both purchases were made in, say, January 2027, only £1m of AIA would be available and the remaining £800,000 would trickle through the 18% main pool at a much slower rate:

• Year 1 pool allowance at 18%: £144,000
• Year 2: £117,720
• And so on, taking many years to fully deduct

Timing the split of a large purchase across a year-end can therefore save significant tax earlier, improving cash flow.

The reverse timing problem occurs when the AIA limit is reached mid-year. A company that makes all its capital spend in April risks having no AIA left for a large unexpected purchase in February. Planning your capital expenditure pipeline throughout the year is important.

Capital Allowance Pools: Main and Special Rate

When expenditure exceeds the AIA limit, or for assets that do not qualify for AIA (such as cars), costs go into capital allowance pools.

Main pool: Receives the writing down allowance (WDA) at 18% per year on the reducing balance. Assets in the main pool include most general plant and machinery.

Special rate pool: Receives WDA at 6% per year on the reducing balance. Applies to:

• Integral features of buildings (electrical systems, water systems, heating, lifts)
• Long-life assets (economically useful life of 25 years or more)
• Solar panels (from April 2012 onwards)

The reduced 6% rate for special rate assets reflects their long useful lives. However, crucially, special rate pool assets can still be covered by AIA -- allocating the AIA to special rate assets first is often the best strategy, since the WDA on these assets is otherwise so slow.

Small pool WDA: If the balance in the main or special rate pool is below £1,000, you can claim the entire balance in one go rather than applying the standard percentage.

Disposals: When an asset in a pool is sold, the proceeds are deducted from the pool balance. If the pool goes negative (more received than remaining balance), a "balancing charge" arises -- effectively clawing back the excess relief given. If an asset is disposed of for more than the pool balance, this creates a taxable balancing charge.

Full Expensing vs AIA for Incorporated Businesses

From April 2023, incorporated businesses (limited companies) can claim full expensing alongside AIA. Full expensing gives:

• 100% first-year allowance on qualifying new main pool plant and machinery (no £1m cap)
• 50% first-year allowance on qualifying new special rate pool assets (no £1m cap)

Full expensing has no annual limit, so for large capital programmes it is more powerful than AIA alone. However, it has important restrictions that AIA does not:

• Only available to incorporated companies -- not sole traders or partnerships
• Only applies to new assets, not second-hand equipment
• Not available for assets bought for leasing to third parties

AIA remains the go-to relief for unincorporated businesses and for second-hand assets in all businesses. For incorporated companies making substantial new asset purchases, full expensing and AIA can be used together to maximise the relief claimed in the year.

Group Company Rules and Sharing the AIA

Connected companies and businesses under common control can only claim one £1m AIA between them. The rules for connection are broadly the same as for corporation tax group relief: companies are connected if one controls the other, or both are controlled by the same persons.

Critically, the group can choose how to allocate the £1m AIA between the connected entities. The most tax-efficient approach is typically to allocate the AIA to the company or business with the highest marginal tax rate -- either because it is most profitable (paying corporation tax at 25%), or because it is at the top of the marginal relief taper between £50,000 and £250,000.

A group of three connected companies each spending £400,000 on assets in a year cannot each claim £400,000 of AIA (£1.2m total). They share one £1m limit, allocated in whatever split the group chooses -- for example, £500,000 to Company A, £300,000 to Company B, and £200,000 to Company C. Each company's excess above its allocated AIA goes into its own capital allowances pool.

Planning the timing of capital expenditure across a corporate group, and the allocation of AIA within the group, requires coordinated advice across the group's accounting periods. The potential tax value of getting this right on a large capital programme is substantial.