Capital Allowances on a Solar Carport

Which pool a solar carport falls into

Solar panels have been special-rate expenditure since April 2012, under CAA 2001 s104A(1)(g). That is the fact everything else follows from. Special-rate expenditure is written down at 6% a year; the main pool rate is 14% from April 2026 (18% before). The structural steel, groundworks and electrical installation of a carport are part of the same capital project but are not automatically in the same pool as the panels, so ask your accountant to split the invoice by asset rather than accepting one line.

The Annual Investment Allowance is the main route

The AIA gives 100% relief in year one on up to £1m of qualifying expenditure a year. Two points are often missed: it covers special-rate expenditure, so it reaches the panels, and it is available to companies and unincorporated businesses alike — sole traders, partnerships and LLPs. HMRC's guidance (CA23084) also confirms the taxpayer may allocate the AIA across qualifying expenditure as they choose, so it is usually pointed at the special-rate items first, because those would otherwise be relieved at 6%.

On a £300,000 carport, a company paying corporation tax at 25% takes a £300,000 deduction in year one, worth £75,000 of tax. That is the honest number. It is not the same as the project costing £225,000.

Above the £1m cap: the 50% first-year allowance

Where a scheme takes total qualifying spend past the AIA cap, a company can claim a 50% first-year allowance on the special-rate balance, with the remaining 50% added to the special-rate pool and written down at 6% thereafter. Unincorporated businesses cannot use the 50% FYA. There is no 100% route above £1m for solar.

Full expensing does not apply to solar — and nor does the 40% FYA

This is the most common error in commercial solar copy, and it changes purchase decisions. GOV.UK states that companies cannot claim full expensing for special-rate assets, naming solar panels and assets with an expected life of at least 25 years, and directs them to the 50% special-rate allowance instead.

The 40% first-year allowance introduced on 1 January 2026 is main-rate only. It does not reach a solar carport either. If a supplier's proposal shows 100% first-year relief above £1m, or cites the 40% allowance for the panels, the tax line in that model is wrong.

Enhanced Capital Allowances ended in April 2020

The Energy Technology List route — the original ECA for energy-efficient plant — ended in April 2020. Being listed on the ETL confers no allowance today, and any page explaining how to claim it is describing a relief withdrawn six years ago. The exception that is not an error: Freeport and Investment Zone enhanced capital allowances are a separate, live relief for new plant in a designated tax site, so a scheme inside one of those sites should be checked against it.

What to hand your accountant

Five things make the claim straightforward: an invoice broken down by asset (panels, inverters, steelwork, groundworks, electrical, EV provision); the commissioning date, which fixes the accounting period; the G99 connection paperwork; confirmation of whether the asset sits in a taxable entity at all, because a charity or a non-taxpaying public body gets nothing from the AIA and should look at funding structures instead; and the total qualifying spend for the year, which decides whether the £1m cap binds. Where the entity cannot use allowances, a PPA shifts the capital allowances to the funder, whose tariff should reflect it.

Why the allowance matters more now

With the government's solar canopy mandate shelved (the 21 May 2026 outcome), nothing forces a car park owner to act, and the Annual Investment Allowance is one of the few levers that changes the payback of a voluntary scheme. Check the position with your accountant before pricing, and read why more UK car parks do not have solar for the other factors that decide a scheme.