AIA & Solar
Annual Investment Allowance for Solar PV — 2026 UK Tax Guide
AIA gives UK companies 100% first-year tax deduction on commercial solar PV up to £1m per year. Full Expensing extends this for limited companies. Post-tax effective solar cost drops by 25%.
100%
First-year deduction
£1m
AIA cap (2026)
25%
Post-tax cost cut
Full Expensing
Limited Co. extension
Annual Investment Allowance (AIA) is the most material tax incentive for UK commercial solar in 2026. It allows full deduction of solar PV capital cost from taxable profit in the year of installation — for most commercial buyers, that's a 25% reduction in post-tax effective system cost. Full Expensing extends similar treatment for limited companies. Here's how it works.
What Qualifies as AIA-Eligible Solar Expenditure
- Solar PV panels
- Inverters (string, central, microinverters, optimisers)
- Mounting and racking systems
- DC and AC cabling
- Junction boxes, isolators, fuses
- Monitoring systems
- Design and engineering fees (HMRC accepts these as part of capital expenditure)
- DNO connection costs
- Installation labour
- Commissioning costs
- Battery storage where installed alongside solar (under HMRC's 2024 confirmation)
What Does NOT Qualify
- Roof repairs unrelated to solar (separately treated)
- Site groundworks unrelated to solar (e.g. car park resurfacing)
- Solar PPA payments (these are operating expenditure, not capital)
- Insurance premiums for the solar system
- O&M contract fees (operating cost)
How AIA Works — Worked Example
Limited company installs a 100kW solar system at £100,000 capital cost.
- Year-1 taxable profit (before AIA): £400,000
- AIA claimed against solar: £100,000
- Year-1 taxable profit (after AIA): £300,000
- Year-1 corporation tax (25%): £75,000 (vs £100,000 without AIA)
- Tax saving from AIA: £25,000
- Post-tax effective cost of solar: £100,000 − £25,000 = £75,000
AIA Cap and Annual Limit
- 2026 AIA cap: £1,000,000 per year (per company / group)
- Solar systems above £1m capital cost split across more than one tax year, or use Full Expensing for limited companies.
- The £1m cap is shared across all qualifying capital expenditure (not just solar).
Full Expensing — The Extension
Full Expensing (made permanent in 2024) allows limited companies to claim 100% deduction on main-pool plant and machinery — including solar PV — without the £1m cap. Effectively, FE replaces AIA for limited companies on solar PV (and most other commercial capital):
- 100% first-year deduction
- No cap
- Available to limited companies (not sole traders or partnerships)
- Permanent (post-2024 reforms)
Sole Trader and Partnership AIA
- AIA still applies (£1m cap).
- Full Expensing not available — limited to incorporated companies.
- Income tax rate at the top: up to 45% (Scotland: 47%) — depending on personal income, the post-tax effective cost can drop further than for limited companies.
Battery Storage and AIA — Important Update
HMRC confirmed in 2024 that battery storage installed alongside (and operationally integrated with) solar PV qualifies for AIA / Full Expensing. Standalone batteries (no solar) have a more nuanced position. We work with our clients' accountants on the specific qualifying status.
How to Claim AIA on Solar
- Confirm with your accountant the company's qualifying status.
- Complete capital expenditure pages of the company's CT600 corporation tax return.
- Maintain detailed install invoice + commissioning evidence (we provide this as standard).
- Submit return; AIA is claimed in the period of expenditure.
- Tax saving accrues in the same accounting period.
Frequently Asked Questions
Does commercial solar qualify for AIA?
Yes. UK commercial solar PV qualifies for Annual Investment Allowance, providing 100% first-year deduction against taxable profit up to £1m per year. Full Expensing extends this for limited companies.
What's the difference between AIA and Full Expensing?
AIA: £1m annual cap, available to all businesses. Full Expensing: no cap, available to limited companies only. Both provide 100% first-year deduction on qualifying solar capital. Limited companies typically use Full Expensing above the AIA cap.
Can AIA be claimed on solar batteries?
Yes — HMRC confirmed in 2024 that battery storage installed alongside solar PV qualifies for AIA / Full Expensing. Standalone batteries without solar have a more nuanced position; consult your accountant.
What about VAT on commercial solar?
Commercial solar PV currently attracts 0% VAT under the 2022–2027 zero-rating extension. This is separate from AIA and applies regardless of business structure.
Can a sole trader claim AIA on solar?
Yes — sole traders and partnerships can claim AIA up to the £1m cap. Sole traders cannot use Full Expensing (limited to incorporated companies). Income tax rates may make sole-trader AIA highly tax-effective at the upper income brackets.
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AIA Solar: Worked Examples for Different Business Types
The Annual Investment Allowance's impact varies significantly depending on company size, tax rate and installation cost. Understanding the real numbers is essential for accurate project appraisal.
**Small company (19% corporation tax, £80,000 installation):** AIA deduction: £80,000. Tax saving: £15,200. Net cost after AIA and VAT saving (0%): £64,800. Year-1 energy saving: £14,000. Net first-year position: £50,800 invested, £14,000 returned. IRR over 25 years: approximately 20%.
**Medium company (25% corporation tax, £300,000 installation):** AIA deduction: £300,000 (within £1M AIA limit). Tax saving: £75,000. Net cost after AIA and VAT saving: £225,000. Year-1 energy saving: £52,000. Net first-year position: £173,000 invested, £52,000 returned. IRR over 25 years: approximately 24%.
**Large company (25% corporation tax, £800,000 installation — farm or industrial estate):** AIA deduction: £800,000 (within £1M AIA limit). Tax saving: £200,000. Net cost after AIA and VAT saving: £600,000. Year-1 energy saving: £140,000. Net first-year position: £460,000 invested, £140,000 returned. Payback: 3.3 years. IRR: approximately 28%.
AIA vs Full Expensing: Which is Better for Solar?
From April 2023, the UK government introduced 'Full Expensing' — 100% first-year relief on qualifying plant and machinery for incorporated businesses (limited companies). Full Expensing works similarly to AIA for solar investments: you can deduct 100% of the cost from pre-tax profits in the year of purchase. The difference is that Full Expensing has no annual cap (unlike AIA's £1M limit) — for very large solar investments above £1M, Full Expensing is the relevant relief.
For most commercial solar projects under £1M, AIA and Full Expensing are functionally identical in their tax impact. The AIA limit of £1M per year (per business, or per group for connected businesses) is sufficient to cover the full cost of all but the very largest single commercial solar installations — a 1MW solar system at £500,000-£700,000 is well within the AIA annual limit.
Can sole traders and partnerships claim AIA on commercial solar?
Yes — sole traders and partnerships can claim Annual Investment Allowance on commercial solar panels installed for business use. The AIA annual limit of £1M applies per business, irrespective of legal structure. Sole traders and partnerships deduct the AIA from their taxable business profits via their Self Assessment tax return. The mechanism is the same as for limited companies: 100% of the qualifying expenditure is deducted from taxable profits in the year of purchase, reducing the tax bill by 20% (basic rate taxpayers) or 40-45% (higher rate taxpayers).