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. Above the cap, a 50% first-year allowance covers solar's special-rate spend. Post-tax effective solar cost drops by 25%.
100%
First-year deduction
£1m
AIA cap (2026)
25%
Post-tax cost cut
50% FYA
Above-cap 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. Above the £1m cap, a 50% first-year allowance covers the excess. 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 claim the 50% first-year allowance on the excess.
- The £1m cap is shared across all qualifying capital expenditure (not just solar).
Full Expensing Does Not Apply to Solar — Here's Why
Full expensing does not apply to solar PV — HMRC classes solar as special rate expenditure, and full expensing (made permanent in 2024) covers main rate plant and machinery only. What actually happens above the AIA cap:
- AIA absorbs the first £1m at a 100% first-year deduction
- A 50% first-year allowance applies to special-rate solar spend beyond the AIA (limited companies)
- The remaining balance enters the special rate pool at 6% writing down allowances
- Sole traders and partnerships stay on the AIA and writing down allowances
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. Standalone batteries (no solar) have a more nuanced position — one to confirm with your accountant before you commit.
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 does not apply to solar (special rate expenditure) — above the AIA cap, a 50% first-year allowance covers the excess.
What's the difference between AIA and Full Expensing?
AIA: £1m annual cap, available to all businesses, 100% first-year deduction. Full expensing: no cap, limited companies only — but it covers main rate assets, and solar is special rate expenditure, so it does not apply to solar. Above the AIA cap, solar spend qualifies for a 50% first-year allowance instead.
Can AIA be claimed on solar batteries?
Yes — HMRC confirmed in 2024 that battery storage installed alongside solar PV qualifies for AIA. Standalone batteries without solar have a more nuanced position; consult your accountant.
What about VAT on commercial solar?
Commercial solar installations are standard-rated for VAT (20%), which VAT-registered businesses recover in the normal way. The 0% VAT relief applies to domestic installations only, and runs until 31 March 2027.
Can a sole trader claim AIA on solar?
Yes — sole traders and partnerships can claim AIA up to the £1m cap. Full expensing does not apply to solar in any case (special rate expenditure), and is limited to incorporated companies. Income tax rates may make sole-trader AIA highly tax-effective at the upper income brackets.
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