Commercial Solar Tax Relief 2026: AIA, Allowances and VAT

Getting the tax position right on a commercial solar installation changes the real cost of the project, sometimes by tens of thousands of pounds. The rules are widely misreported online, so this guide sets out the correct position for UK businesses in 2026 and shows where the common myths trip people up.

This is general information, not tax advice. Your own position depends on your business structure, profits and accounting period, so confirm the detail with your accountant before you commit.

Solar PV is special-rate plant, and why that matters

The single most important fact is that solar photovoltaic equipment is classed as special-rate plant and machinery for capital allowances. It sits in the same pool as things like electrical systems and integral building features, not in the main pool.

This classification is the reason so much online advice is wrong. Special-rate assets are treated differently from ordinary plant, and that difference is where most of the confusion comes from.

The full-expensing myth

You will often see solar sold on the promise of “100% full expensing” or the newer “40% first-year allowance”. Both are real reliefs, but neither applies to solar.

Full expensing gives a 100% first-year deduction for main-rate plant only. Because solar is special rate, it is specifically excluded. The 40% first-year allowance that succeeds full expensing is likewise a main-rate relief and does not cover solar either. Anyone telling you a rooftop array qualifies for full expensing is quoting the wrong rule.

The relief that does apply: the Annual Investment Allowance

The good news is that solar qualifies comfortably for the Annual Investment Allowance (AIA). The AIA gives a 100% first-year deduction on qualifying capital spend up to £1m per accounting period, and that £1m limit covers the great majority of commercial installations outright.

In practice, if your solar spend and any other qualifying capital expenditure in the year stay within the AIA limit, you deduct the full cost from your taxable profits in year one. That is the same headline outcome as full expensing, reached through the correct route.

Above the AIA cap

Larger projects, or businesses that have already used their AIA on other assets, can spill over the £1m limit. Companies subject to Corporation Tax can then claim the 50% special-rate first-year allowance on the excess, deducting half the remaining cost in year one. The balance goes into the special-rate pool and is written down at 6% a year on a reducing-balance basis.

Note that the 50% special-rate first-year allowance is available to companies only, not to unincorporated businesses.

Relief routes at a glance

Route	What it gives	Applies to solar?
Annual Investment Allowance	100% relief on up to £1m of spend	Yes, and covers most installs
Full expensing (100%)	100% first-year deduction, main-rate only	No, solar is special rate
40% first-year allowance	Main-rate first-year relief	No, solar is special rate
50% special-rate FYA	50% first-year deduction, companies only	Yes, on spend above the AIA cap
Writing-down allowance	6% a year, reducing balance	Yes, on any unrelieved balance

Because the choice of ownership route affects who can claim what, it is worth modelling the tax outcome alongside the finance decision. Our finance calculator and the finance options compared page help you see how a capital purchase, a lease and a loan stack up once relief is factored in.

VAT on commercial solar

Commercial solar is standard-rated at 20% VAT. The 0% rate that applies to domestic installations does not extend to commercial premises, so ignore any suggestion that your business install is zero-rated.

For a VAT-registered business this is usually neutral in the long run, because you reclaim the input VAT in the normal way through your VAT return, subject to the usual rules on business use. Where a site has mixed or partly exempt use, the recoverable amount may be restricted, which is another point to check with your accountant.

Business rates exemption

There is a further, often overlooked, saving. In England, eligible rooftop solar installed for self-consumption is 100% exempt from business rates from 1 April 2022 to 31 March 2035. In other words, generating power to run your own site does not add to your rateable value during that window.

This exemption strengthens the case for self-consumption designs, where you size the system to match your daytime load rather than to export.

Exported power and the Smart Export Guarantee

Any electricity you do not use on site can be exported. The Smart Export Guarantee (SEG) replaced the old Feed-in Tariff and pays for exported units, with installations up to 5 MW eligible. Rates vary between suppliers, so SEG income tends to be a useful top-up rather than the core of the business case. For most commercial sites the strongest return comes from displacing grid electricity through self-consumption.

Public sector organisations should note that schemes such as Salix funding and the Public Sector Decarbonisation Scheme are restricted to the public sector and are not open to private businesses. If you sit in that category, our grants and funding page is the place to start.

Putting the tax position into the numbers

Tax relief is only one lever. The overall return on a commercial installation also depends on system cost, self-consumption rate, energy prices and how you fund the project. A capital purchase captures the allowances directly on your own balance sheet, while an off-balance-sheet route such as a power purchase agreement shifts ownership and the allowance claim to the funder, with you buying the generated power instead.

To see how the reliefs feed through to a real figure, work through our cost and payback and ROI pages, which set out typical ranges and the drivers behind them.

How to compare your options

The best route depends on your tax position, cash flow and whether you want to own the asset. A profitable company with headroom under its AIA often does best owning outright and claiming the full first-year deduction. A business wanting to protect cash may prefer hire purchase, asset finance or a no-upfront-cost arrangement, accepting a different tax treatment in exchange for spreading the outlay.

We are a comparison and quote service, not a lender or financial adviser. We connect UK businesses with vetted, MCS-certified installers and funders so you can compare fully costed finance quotes across every route side by side.

Get costed quotes

If you want to see how the tax reliefs and finance routes translate into a real number for your building, request a set of costed quotes. Tell us your site and load, and we will return comparable figures from vetted installers and funders so you can decide with the full picture in front of you.

Confirm the tax detail with your accountant, then get your quotes to move from theory to firm numbers.