Full Expensing lets UK companies deduct 100% of qualifying plant and machinery capex, including commercial solar PV, from taxable profits in the year of purchase. At the 25% main rate of Corporation Tax, that's a quarter of your system cost back inside 12 months.
A £400,000 rooftop solar system installed by a profitable UK Ltd:
The deduction is claimed in the accounting period the expenditure is incurred. If you commission a system in month 11 of your financial year, the tax relief lands in that year's return, not the next.
This page is a plain-English summary, not tax advice. Always confirm eligibility and treatment with your accountant or tax adviser before committing capex.