Glossary · UK
What is Annual Investment Allowance (AIA)?
A capital allowance giving businesses 100% tax relief in the year of purchase on qualifying plant and machinery expenditure up to an annual limit of 1 million pounds, allowing the full cost to be deducted from taxable profits immediately.
Full Definition
The Annual Investment Allowance (AIA) allows businesses -- sole traders, partnerships, and companies -- to deduct the full cost of qualifying capital expenditure on plant and machinery from their taxable profits in the year of purchase, up to an annual limit of 1 million pounds, rather than spreading the tax relief over several years through the ordinary, slower writing down allowances. Qualifying expenditure includes most equipment, machinery, computers, commercial vehicles, and fixtures integral to a building (such as electrical and heating systems), though it specifically excludes cars (which instead qualify for separate capital allowances based on CO2 emissions) and land and buildings themselves. Because the AIA gives 100% relief immediately, rather than the 18% or 6% annual writing down allowances that otherwise apply to most plant and machinery, it significantly accelerates the tax benefit of business investment, improving cash flow in the year of purchase, particularly valuable for smaller and medium-sized businesses whose qualifying expenditure typically falls well within the 1 million pound annual limit. Expenditure above the AIA limit in a given accounting period, or expenditure on assets that do not qualify for AIA (such as cars), instead goes into the main rate pool (18% writing down allowance per year, on a reducing balance basis) or the special rate pool (6% writing down allowance per year) depending on the asset type. The AIA limit has changed several times since its introduction in 2008, at various points falling as low as 25,000 pounds and rising as high as 1 million pounds, before being made permanent at the 1 million pound level from 1 April 2023, giving businesses more certainty for long-term capital investment planning than the previous pattern of temporary, time-limited increases. Businesses with accounting periods spanning a change in the AIA limit, or groups of connected companies (which must share a single AIA limit between them rather than each company claiming the full amount separately), need to apply specific transitional and apportionment rules to calculate the correct available allowance, making this an area where accountancy advice is often sought for significant capital expenditure decisions.