Maximising Capital Allowances and Niche Construction Tax Reliefs

Construction is one of the most capital-intensive sectors in the UK economy, and yet capital allowance claims in construction are consistently under-optimised. Routine claims miss substantial integral features in commercial fit-outs. Land Remediation Relief on contaminated brownfield sites is rarely claimed. Retrospective claims on historical property acquisitions sit untouched in many balance sheets. The combined under-claim across the sector runs into hundreds of millions per year.

This guide covers the major capital allowance and adjacent reliefs available to UK construction firms, with the technical eligibility tests for each. The work splits into four areas: ordinary capital allowances on plant and machinery (AIA, Full Expensing); niche reliefs (LRR, SBA, R&D); integral features in property; and retrospective claims on historical assets.

Annual Investment Allowance and Full Expensing

The two main routes for first-year capital deduction:

1. 1Annual Investment Allowance (AIA): 100% deduction up to £1,000,000 per year on qualifying plant and machinery. Available to companies and unincorporated businesses.
2. 2Full Expensing: 100% deduction with no upper limit on most main-rate plant and machinery. Available to limited companies only. New equipment only (second-hand goes through AIA or writing-down allowances).
3. 3Special rate pool 50% First Year Allowance: 50% first-year deduction on integral features and long-life assets.
4. 4Annual Allowance writing-down for residual pool balances: 18% main rate, 6% special rate.

Land Remediation Relief (LRR)

LRR provides 150% deduction (or a tax credit for loss-making companies) on qualifying expenditure to remediate contaminated or derelict land. The eligible expenditure includes:

• Removing or treating contaminants (asbestos, hydrocarbons, chemicals from prior industrial use).
• Removing or treating Japanese knotweed and other invasive species.
• Repairing or removing defective foundations.
• Demolition where it is part of remediation.
• Site clearance to enable remediation.

For a development on a brownfield site, LRR can transform the project economics. £500,000 of qualifying remediation produces £750,000 of deductions (150%); for a profitable developer this is £150,000 to £200,000 of corporation tax saving depending on band. Heavily under-claimed in the sector.

Structures and Buildings Allowance (SBA)

SBA provides 3% per year straight-line allowance on the cost of constructing or buying new commercial structures and buildings. Available since October 2018. The eligibility criteria:

• New construction (not residential, not lodgings, not most agricultural).
• Used in a qualifying trade.
• In use after October 2018.
• Costs include construction, refurbishment leading to first use, fit-out costs.

The 3% rate is modest by capital allowance standards but applies to structures that historically had no allowance at all. Over the 33-year writing-down period, the cumulative relief approaches the full cost. For a £10 million commercial building, SBA produces £300,000 of annual deduction for the life of the asset.

Integral features in commercial fit-outs

When acquiring or fitting out commercial property, several elements that look like part of the building actually qualify as plant and machinery (eligible for AIA or special-rate pool). The major categories:

A specialist capital allowances review on a £2 million fit-out routinely identifies £500,000+ of qualifying expenditure that an ordinary accountant would not split out. The relief value is the difference between the allowance pool and the full denial of relief on building elements.

Retrospective capital allowance claims

For commercial property acquired in earlier years where capital allowances were not specifically identified at the time, retrospective claims are often available. The mechanics:

1. 1Specialist surveyor or capital allowances expert reviews the historical purchase contracts and the property itself.
2. 2Identifies qualifying integral features that were embedded in the purchase price but not allocated to plant and machinery.
3. 3Calculates the eligible expenditure under HMRC's rules for retrospective claims.
4. 4Submits the claim either through the next CT600 (where the company still holds the property) or via specific procedures depending on the disposal status.

The claim is subject to strict rules: the property must still be in qualifying use, the expenditure cannot have been claimed by a previous owner, and the claim must fall within applicable time limits. A specialist review on a property bought 5 years ago for £4 million typically identifies £400,000 to £600,000 of unclaimed integral features.