Corporation Tax Disallowances: When Can HMRC Reject a Business Expense Claim?

Every company preparing its corporation tax computation faces the same underlying question: is this expense actually deductible? Most business owners assume that if a cost appears in the company accounts and was genuinely paid for a business reason, it will reduce the taxable profit. In practice, the position is more nuanced. HMRC applies a distinct set of statutory rules when deciding whether an expense claimed for accounting purposes can also be deducted for corporation tax purposes, and a significant proportion of enquiries, discovery assessments, and disputes arise precisely because a business has claimed a deduction that HMRC considers disallowable. Understanding when and why HMRC can reject an expense claim, and how a disallowance can be challenged, is essential for any director, finance function, or accountant managing a company’s tax affairs.

What Does “Disallowance” Actually Mean?

A disallowance occurs when HMRC removes, or “adds back,” an expense that a company has deducted in arriving at its taxable profit. This does not necessarily mean the expense was fraudulent or even improperly incurred from a commercial perspective. It simply means that, in HMRC’s view, the expense fails to meet the specific statutory tests that govern deductibility for corporation tax purposes. The starting point in UK law is that a company’s taxable trading profit is calculated in accordance with generally accepted accounting practice, but that starting figure is then adjusted for tax purposes by adding back items the legislation specifically disallows.

Disallowances typically surface during an HMRC compliance check into a corporation tax return, following a review of the accounts by an HMRC officer, or as part of a wider HMRC investigation. Where a disallowance results in additional tax being due, HMRC will amend the return or, outside the normal enquiry window, may seek to raise a discovery assessment to recover the underpaid tax.

The Core Test: “Wholly and Exclusively” for the Purposes of the Trade

The single most important statutory provision governing business expense deductions is section 54 of the Corporation Tax Act 2009 (CTA 2009). It provides that in calculating the profits of a trade, no deduction is allowed for expenses not incurred wholly and exclusively for the purposes of the trade. The phrase “for the purposes of the trade” has been interpreted by the courts to mean expenditure whose object is to serve the trade itself, rather than expenditure that merely benefits the company or its directors incidentally, or that serves some private or collateral purpose. Where an expense can be shown to have a dual purpose, part business and part private or unconnected with the trade, the whole of the expenditure will generally be disallowed unless a discrete business element can be clearly identified and apportioned.

Importantly for companies, section 54(2) CTA 2009 allows an apportionment where expenditure serves partly the purposes of the trade and partly some other purpose, something not generally available to unincorporated businesses under the equivalent income tax provision. This apportionment mechanism was central to the recent Court of Appeal decision in A D Bly Groundworks and Civil Engineering Ltd v HMRC [2025] EWCA Civ 1443, where the court confirmed that the “wholly and exclusively” test focuses on the object of the expenditure rather than its effect. The Court of Appeal held that where the First-tier Tribunal has found as a fact that an arrangement was adopted predominantly to achieve a tax saving, rather than for a genuine commercial purpose, a section 54 deduction will fail even where the arrangement also delivers some incidental business benefit, such as remunerating employees. The decision is a useful reminder that the underlying object of an expense, established through the evidence available to HMRC and the tribunal, is frequently the decisive factor in these disputes, and that structuring arrangements primarily around tax efficiency carries real risk if the commercial rationale is not clearly evidenced and genuinely primary.

Capital Versus Revenue Expenditure

A second major category of disallowance arises from the capital versus revenue distinction. Section 53 CTA 2009 prohibits a deduction for items of a capital nature in calculating trading profits. Capital expenditure is not lost entirely, since it may qualify for capital allowances instead, but it cannot be deducted as a revenue expense against profits in the way that day to day running costs can.

The general approach taken by HMRC and the courts is that expenditure bringing into existence an asset or advantage for the enduring benefit of the trade is capital in nature, whereas expenditure incurred in the ordinary course of earning profits, such as replacing stock, meeting running costs, or maintaining existing assets, is revenue in nature and deductible. This distinction is not always straightforward to apply. Costs of acquiring premises, extending business capacity, or restructuring a company’s share or loan capital have frequently been treated as capital, even where the company itself regarded the expenditure as necessary to protect or promote its trade. Similarly, professional fees connected with a capital transaction, such as legal and advisory costs on an acquisition or a refinancing, are generally treated as capital in nature and follow the tax treatment of the underlying transaction, rather than being deductible as a routine overhead.

Company directors frequently misclassify significant one-off costs as ordinary business expenses when they in fact relate to the acquisition, improvement, or restructuring of a capital asset or the company’s underlying capital structure. HMRC routinely disallows such items on review, and disputes over the capital and revenue boundary remain among the most common sources of corporation tax adjustment.

Business Entertainment and Gifts

Business entertainment is subject to a specific statutory disallowance under section 1298 CTA 2009, separate from and in addition to the wholly and exclusively test. Even where entertainment expenditure genuinely serves the purposes of the trade and would otherwise satisfy section 54, section 1298 imposes a blanket disallowance on the cost of entertaining clients, suppliers, or other third parties, including any expenditure incidental to that entertainment. The only exceptions are set out in section 1299 CTA 2009, covering entertainment provided in the ordinary course of a business that exists to provide entertainment, and entertainment provided exclusively for a company’s own employees, subject to further conditions. Gifts to customers are similarly disallowed under section 1298, save for limited exceptions in section 1300 CTA 2009 relating to low value branded gifts and free samples of a company’s own products.

This is an area where genuine confusion frequently causes an unintentional understatement of tax, since many businesses assume that any hospitality connected with generating sales is automatically deductible. It is not, and the disallowance applies regardless of how clearly commercial the underlying motive may be.

Other Common Grounds for Disallowance

Beyond the core wholly and exclusively test, the capital and revenue divide, and entertainment expenditure, HMRC commonly raises disallowances in relation to:

1. Provisions and accruals that do not meet the statutory conditions, particularly where a liability is contingent, speculative, or not sufficiently certain to be recognised under generally accepted accounting practice.
2. Payments connected with employee benefit contributions, where section 1290 CTA 2009 restricts deductions unless and until the relevant benefits are actually provided to employees within a specified period, an issue also considered by the Court of Appeal in A D Bly Groundworks and Civil Engineering Ltd v HMRC [2025] EWCA Civ 1443.
3. Excessive or unsubstantiated director remuneration, where HMRC questions whether payments genuinely reflect services rendered to the trade or represent a disguised extraction of profit.
4. Fines and penalties, which are generally disallowable as a matter of public policy, regardless of any connection with the trade.
5. Expenditure lacking adequate documentary evidence, since the burden ultimately rests on the taxpayer to demonstrate both that expenditure was incurred and that it satisfies the relevant statutory tests.

What Happens if HMRC Disallows an Expense?

Where HMRC concludes during a compliance check that an expense has been incorrectly deducted, it will typically propose an amendment to the company’s self assessment, increasing the taxable profit and the resulting corporation tax liability, together with interest and, depending on the circumstances, a penalty for an inaccurate return. Where the enquiry window has already closed, HMRC may instead seek to raise a discovery assessment, a power subject to its own strict conditions and time limits.

A company facing a proposed disallowance is not without recourse. The taxpayer is entitled to challenge HMRC’s conclusion, first through correspondence and an internal HMRC review, and if the matter remains unresolved, by appeal to the First-tier Tribunal (Tax Chamber). Given the highly fact-sensitive nature of the wholly and exclusively test and the capital and revenue distinction, cases frequently turn on the quality of contemporaneous evidence, board minutes, correspondence, and invoices, demonstrating the genuine commercial object behind the expenditure. Early legal advice significantly improves the prospects of assembling the right evidence before HMRC’s position becomes entrenched.

Where a persistent corporation tax liability arising from disallowed deductions leads to enforcement action against the company, including statutory demands or the presentation of a winding-up petition, specialist advice should be sought without delay from a firm experienced in insolvency litigation; see windinguppetitionsolicitors.co.uk for guidance on defending such petitions. Separately, where a disallowance arose because an accountant or tax adviser gave negligent advice on the deductibility of an expense, a company may have a claim in professional negligence against that adviser to recover the resulting tax, interest, and penalties.

Speak to a Specialist Tax Solicitor

Corporation tax disallowances are rarely straightforward, and the correct classification of an expense often depends on subtle distinctions drawn from the underlying legislation and its judicial interpretation. Whether you are responding to an HMRC compliance check, challenging a proposed amendment, or preparing an appeal to the First-tier Tribunal, the strength of your position depends on early, technically rigorous advice.

LEXLAW’s tax disputes team includes solicitors and barristers with direct experience of HMRC’s internal processes, having previously acted as HMRC’s own senior tax counsel, alongside professionals with Big 4 tax litigation backgrounds. Operating from chambers in Middle Temple, London, our lawyers regularly advise companies and directors on disallowed expense claims, discovery assessments, and Tribunal appeals, working to protect both the company’s tax position and, where enforcement action follows, the business itself. For confidential advice on a proposed corporation tax disallowance or HMRC enquiry, contact our specialist tax dispute solicitors today.