AIA 2026 guide — how UK businesses claim 100% first-year tax relief on commercial solar PV up to £1m. Eligibility, calculation worked examples, group cap rules.
The Annual Investment Allowance is a capital allowance that lets UK businesses deduct 100% of the cost of qualifying plant and machinery from their taxable profits in the year of purchase, up to an annual cap of £1 million. It applies to all UK business structures — limited companies, partnerships, sole traders — and to almost any tangible commercial asset including solar PV systems and battery storage.
For solar specifically, the AIA is the workhorse of UK commercial solar tax planning. Full expensing is not an option on solar at any project size — solar panels are special-rate plant and GOV.UK excludes special-rate assets from full expensing — so the AIA covers the entire commercial solar SME market — including the substantial population of farms, hotels and family-run manufacturers that operate as sole traders, partnerships or LLPs and are therefore ineligible for Full Expensing.
| Maximum claim per year | £1,000,000 |
| Effective tax saving (25% CT rate) | Up to £250,000 per year |
| Effective tax saving (19% small CT rate) | Up to £190,000 per year |
| Effective tax saving (sole trader top-rate IT) | Up to £450,000 per year |
| Group cap | £1m shared across all companies in a corporate group |
| Time to benefit | Crystallises at next corporation tax / self-assessment filing |
The AIA is not an application — it is a deduction claimed when you file your tax return. Practical sequence:
Step 1. Your installer issues an invoice clearly itemising the solar PV system as plant and machinery. Have your accountant flag the invoice for the capital allowances pool.
Step 2. At financial year-end, your accountant calculates the AIA available (£1m minus any other AIA claims you have made in the period — for example a fleet vehicle or new plant).
Step 3. The full installation cost (assuming it falls within the AIA cap) is added to the "Annual Investment Allowance" line of your CT600 corporation tax return (Box 725) or your Self Assessment SA100 / SA800.
Step 4. HMRC processes the return — your corporation tax bill for the year is reduced by the AIA claim multiplied by your marginal CT rate. There is no separate HMRC sign-off; the AIA is self-assessed.
Step 5. Keep your installer's invoice, MCS certificate, and commissioning report for six years in case of HMRC enquiry. The Mac-vendor disclosure rules mean HMRC may sample-test claims, especially on large amounts.
Worked example: 100kWp commercial rooftop install, limited company, £95,000 net of VAT.
- Installation cost: £95,000 plus £19,000 VAT (reclaimable for VAT-registered businesses). - AIA-eligible plant and machinery: £95,000 (assumes panels, inverters, mounting, cabling, battery). - AIA deduction: £95,000 (well under the £1m cap). - Corporation tax saved (at 25% main rate): £23,750. - Net effective cost after AIA: £71,250. - 25-year SEG income (assume 1p/kWh average export tariff, 35% export): approx. £8,400. - 25-year self-consumption savings (assume 28p/kWh import, 65% self-consumed): approx. £490,000 (undiscounted).
Net IRR after AIA: ~17%. Payback: 4.5–5.5 years.
Worked example: 80kWp ground-mount, sole trader farm, £72,000.
- Sole trader at higher rate IT (45%): AIA saving £32,400. - Net effective cost: £39,600. - Payback drops below 4 years if SEG income is reinvested.
AIA vs Full Expensing — which to use?
- Limited companies can use either, and Full Expensing is uncapped, so for installations over £1m, Full Expensing wins decisively. - For installations under £1m, the cash effect is identical — both deliver 100% first-year deduction. The difference is in disposal: AIA has a balancing charge over 8 years; Full Expensing has an immediate balancing charge of 100% of disposal proceeds (so disposal is taxed in full). - Sole traders, partnerships and LLPs cannot use Full Expensing. AIA is the only 100% FYA route available. - Most commercial solar SMEs use AIA because (a) their installs are well under £1m, and (b) they want to retain flexibility on disposal treatment.
If your project is between £750k and £1m, always model both routes with your accountant — the AIA cap interacts with other plant purchases and the group cap in ways that can flip the answer.
Most successful 2026 commercial solar projects use a combination of schemes — this is where independent advice earns its keep. Annual Investment Allowance for business solar typically combines well with:
Solar panels are special-rate plant, so companies cannot claim 100% full expensing on them. HMRC allows the 50% first-year allowance instead...
Not available on solar panels. AIA 100% up to £1m, or the 50% special-rate first-year allowance
Smart Export Guarantee 2026 guide for UK businesses — best export tariffs, eligibility for 50kWp+ systems, how to register, and how to combi...
3p–15p per kWh exported (2026 fixed tariffs)
The Energy Technology List route to Enhanced Capital Allowances ended in April 2020. What replaced it for commercial solar: AIA, the 50% fir...
Withdrawn April 2020 — claim AIA or the 50% first-year allowance instead
The Annual Investment Allowance is a capital allowance that lets UK businesses deduct 100% of the cost of qualifying plant and machinery from their taxable profits in the year of purchase, up to an annual cap of £1 million. It applies to all UK business structures — limited companies, partnerships, sole traders — and to almost any tangible commercial asset including solar PV systems and battery storage.
As of May 2026, the scheme's funding status is: Permanent (no expiry currently announced). We re-check application windows monthly — if this is critical to your planning, request an eligibility check for the current programme status.
Typical award range: Up to £1 million per year, 100% first-year deduction. The size of any individual award depends on project capex, sector eligibility, match funding available and the scheme's per-applicant cap.
HMRC — claimed through Corporation Tax or Self Assessment. Applications are submitted through the administrator's process — we link the relevant gov.uk and scheme pages at the bottom of this guide.
The £1m AIA cap is shared across a group of companies. If your parent company has used £900k of AIA on machinery, you only have £100k of AIA headroom for your solar project. Plan around this. Sole traders who go limited mid-project can lose AIA timing. The relief must be claimed in the same accounting period the asset is brought into use — straddling incorporation can create awkward apportionment. Mixed-use property complicates AIA. If you install solar on a property that is partly residential, you can only claim AIA on the commercial portion. This is a common issue for pubs with letting rooms and farms with farmhouse-attached barns.
Tell us your business — we map every active 2026 grant to your sector, size and postcode, and tell you which ones stack.
Free 60-second eligibility check tells you whether Annual Investment Allowance for business solar applies — and which other schemes can stack.
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