Glossary · UK
What is Main Pool (Plant and Machinery)?
The 18% writing-down allowance pool for most business plant and machinery expenditure not in a special rate pool.
Full Definition
The main pool is the primary capital allowances pool for plant and machinery used in a business. Expenditure on qualifying assets is added to the pool and an 18% writing-down allowance (WDA) is claimed each year on the pool balance, reducing the taxable profit. Assets that do not qualify for the Annual Investment Allowance (AIA) or First Year Allowances fall into either the main pool or the special rate pool. The main pool covers most general plant and machinery, computers, vehicles (other than cars with high CO2 emissions), and office equipment. For 2026/27 the AIA provides a 100% first-year deduction on qualifying expenditure up to £1,000,000, meaning most SME spending on plant and machinery can be fully deducted in year one.