Solar PV Capital Allowances: 25% Tax Relief for UK Businesses
For UK businesses, the main route to tax relief on a commercial solar PV system is the Annual Investment Allowance (AIA): it lets you deduct 100% of the install cost (up to £1 million a year) from your taxable profits in the year you buy. Solar is a ‘special rate’ asset, so it does not qualify for 100% full expensing or the new 40% first-year allowance. The cash value of the relief is your tax rate (19–25% for companies) times the cost.
Important — general information, not tax or financial advice. Spectrum Energy Systems Ltd installs solar; we are not tax or financial advisers. Capital allowances depend on your circumstances and on current HMRC rules, which change. The figures below are illustrative. Confirm your position with your accountant and the relevant gov.uk guidance before relying on it.
Commercial solar is one of the few business investments where the taxman effectively pays for a chunk of it. Get the capital allowances right and a £50,000 system can have a post-tax cost closer to £37,500. Get them wrong (and plenty of solar adverts do) and you either overstate the relief to a client or miss it altogether. Here is how it actually works in 2026, in plain English.
In this guide
Which allowance applies to solar: the short version
Solar PV qualifies as plant and machinery, so it attracts capital allowances. But HMRC puts solar in the special rate pool, and that classification decides which reliefs you can use. The practical upshot is simple: the Annual Investment Allowance is your 100% route. Full expensing and the new 40% first-year allowance are both main-rate-pool reliefs, and they exclude special-rate assets like solar.
The Annual Investment Allowance (AIA): your 100% route
The Annual Investment Allowance gives 100% relief on qualifying plant and machinery, up to £1 million per year, deducted from taxable profits in the year of purchase. It is available to sole traders, partnerships and companies, and solar PV qualifies. Because most commercial installs cost well under £1 million, AIA writes off the whole system in year one for the vast majority of businesses.
Two things to watch. The £1 million limit is shared across all your qualifying capital spending in the year, not just solar, so a big year of investment can use it up. And for groups, the limit is divided among associated companies. Full detail is in the gov.uk Annual Investment Allowance guidance.
Why solar doesn’t get ‘full expensing’
This is where a lot of solar marketing is wrong. Full expensing is a permanent 100% first-year allowance, introduced in April 2023, but it applies only to main-rate plant and machinery, and only to companies. HMRC treats solar panels as special-rate expenditure, which full expensing specifically excludes. So when an advert promises ‘100% full expensing on solar’, that is usually inaccurate.
It rarely matters in practice, because AIA already gives you 100% in year one. Full expensing only becomes relevant once AIA is exhausted, and even then, solar doesn’t qualify for it.
The new 40% first-year allowance, and why it skips solar
From the Autumn Budget 2025, a new permanent 40% first-year allowance applies to main-pool plant and machinery from 1 January 2026, for both companies and unincorporated businesses. It is genuinely useful, but it excludes the special-rate pool. Because solar is special-rate, the 40% allowance does not apply to it.
One related change worth knowing: from April 2026 the writing-down allowance on the main pool falls from 18% to 14%, while the special-rate pool (where solar’s residual value sits) stays at 6%. The detail on first-year allowances is set out in the gov.uk full expensing and first-year allowance guidance.
Planning a commercial install?
We give you a clear written quote with the full system cost, so you and your accountant have an exact figure to run the allowances against. No pressure, and we don’t sell finance or tax advice.
See Commercial SolarBeyond £1m: the 50% first-year allowance for companies
If a company’s qualifying spend in a year tops the £1 million AIA limit, the leftover solar spend can use the 50% first-year allowance for special-rate assets: deduct 50% in year one, with the remaining 50% added to the special-rate pool and written down at 6% a year afterwards. Like full expensing, the 50% allowance is for companies (corporation tax) only, and it was made permanent in 2023. Most SME installs never reach this point; AIA covers them in full.
What the relief is actually worth
Capital allowances reduce your taxable profit; the cash in your pocket is your tax rate multiplied by the deduction. For companies in 2026 the corporation tax rates are:
- 25% main rate on profits above £250,000
- 19% small profits rate on profits up to £50,000
- Marginal relief tapering between £50,000 and £250,000
So the ‘effective discount’ on a commercial install runs from 19% to 25% for companies, depending on your profit band (see the gov.uk corporation tax rates).
Worked example (illustrative)
A £50,000 commercial install, bought by a company in the 25% band and claimed in full under AIA, cuts taxable profit by £50,000. That saves £12,500 in corporation tax, so the effective net cost is £37,500. A company in the 19% band would save £9,500 (net £40,500). Your payback maths should run on the post-relief figure, not the headline price. Figures are based on current HMRC rates and assume sufficient taxable profit; your accountant will confirm your position.
For scale: on a recent 49.68kWp commercial system priced around £37,000 plus VAT, a company in the 25% band claiming AIA would see roughly £9,250 of corporation tax relief against the net cost.
Sole traders and partnerships
Unincorporated businesses claim through AIA too (100% up to £1 million), but the cash value is set by your income tax band, not corporation tax. The company-only reliefs (full expensing, the 40% and 50% first-year allowances) don’t apply to sole traders or partnerships, so AIA is your route. It usually covers a typical install in full. Talk to your accountant about timing the spend against your income.
VAT on commercial solar (it’s not 0%)
Domestic solar carries 0% VAT until 31 March 2027. Commercial installs do not; they’re standard-rated at 20% VAT. A VAT-registered business normally recovers that VAT, and capital allowances are then claimed on the net-of-VAT cost. If you’re a homeowner rather than a business, the domestic side is covered in our 0% VAT on solar panels guide.
Timing your spend
Step 1: Know when the relief lands
Allowances are claimed in the accounting period the expenditure is incurred, broadly when you become obliged to pay, not necessarily when cash leaves the account.
Step 2: Align with your year-end
Bringing an install into the current accounting period can pull the relief forward a full year. A short delay can push it back twelve months.
Step 3: Check your total capex against £1m
If you’ve made other large purchases in the year, confirm there’s AIA headroom left before assuming solar gets the full 100%.
This is exactly the sort of thing we’ll talk through when we quote a commercial system: a clear written price and the capex-timing picture, so you can plan the spend with your accountant.
FAQs
Do solar panels qualify for capital allowances?
Yes. Commercial solar PV is plant and machinery, so it qualifies, sitting in the special rate pool. Most businesses claim 100% of the cost in year one through the Annual Investment Allowance (up to £1 million). Homeowners don’t claim capital allowances; domestic installs get 0% VAT instead.
Can I claim full expensing on solar panels?
Generally no. Full expensing is a 100% first-year allowance for main-rate plant and machinery, and for companies only. HMRC treats solar as special-rate expenditure, which full expensing excludes. The 100% relief on solar comes from the Annual Investment Allowance, not full expensing.
Does the new 40% first-year allowance cover solar?
No. The 40% first-year allowance introduced from 1 January 2026 applies to main-pool assets only and excludes the special-rate pool. Solar is special-rate, so it isn’t eligible. Use the Annual Investment Allowance for the 100% year-one deduction instead.
How much tax will I actually save?
The cash value is your tax rate times the deduction. A company in the 25% main rate saves £25,000 of tax on a £100,000 deduction; a 19% small-profits company saves £19,000. Sole traders save at their income tax rate. Confirm the exact figure with your accountant.
Can sole traders and partnerships claim?
Yes, through the Annual Investment Allowance (100% up to £1 million). The company-only reliefs (full expensing and the 40% and 50% first-year allowances) don’t apply to unincorporated businesses, but AIA usually covers a typical install in full.
Do I pay VAT on a commercial solar install?
Yes. Commercial solar is standard-rated at 20% VAT, unlike domestic installs (0% until 31 March 2027). A VAT-registered business normally recovers that VAT, and capital allowances are claimed on the net-of-VAT cost.
Can I claim allowances on a battery or EV chargers too?
Battery storage and EV chargers are plant and machinery and generally qualify, with battery storage also treated as special-rate. The same ‘AIA first’ logic applies. Your accountant will confirm what’s in scope for your specific project.
Related reading
- Solar panel finance UK: pay-monthly options explained
- 0% VAT on solar panels: what homeowners need to know
- Are solar panels worth it in 2026?
For the full commercial picture, see our commercial solar overview.
Speak to Spectrum Energy Systems
MCS NIC200223. RECC 00080159. We design and install commercial solar across the East Midlands and give you a clear written quote, so you and your accountant can work the capital allowances on real numbers. We don’t sell finance or tax advice.
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