20 Feb 2026 2 min read Business Expenses

What Is a Business Expense and What Isn't for UK Tax Purposes?

Understanding exactly what counts as a deductible business expense in the UK — and what HMRC will not allow — is key to accurate tax returns.

Not everything you spend money on as a business owner reduces your tax bill. HMRC has strict rules about what qualifies as a business expense, and misclassifying personal expenditure as business costs is one of the most common audit triggers. Understanding the principles clearly will help you claim what you are entitled to — and no more.

The Fundamental Test

For self-employed people (sole traders and partnerships), the test is set out in the Income Tax (Trading and Other Income) Act 2005: an expense must be incurred wholly and exclusively for the purposes of the trade. For companies, the Corporation Tax Act 2009 uses similar language. 'Wholly and exclusively' means that if an expense has any personal element — even partially — it is not deductible unless a clear business portion can be separately identified.

Clear Business Expenses (Always Allowable)

Office rent, business rates, and utilities for business premises. Wages, salaries, and employer NI for staff. Raw materials, stock, and goods for resale. Professional fees for accountancy, legal work directly related to the business, and specialist advice. Business insurance premiums. Dedicated business phone and internet costs. Advertising and marketing directly promoting the business. Business bank charges and loan interest.

Clear Personal Expenses (Never Allowable)

The ordinary cost of commuting between home and a fixed workplace. Personal clothing (unless a uniform or protective equipment that cannot reasonably be worn outside work). Ordinary food and drink (your own meals while at your usual workplace). Personal use of a vehicle claimed under the actual costs method. Fines, including parking fines incurred while on business. Your personal mortgage or rent for your home (though a proportional home office cost may be allowable).

Common Grey Areas

Client Entertainment

Client entertainment is specifically disallowed for tax purposes — this covers meals, drinks, events, and hospitality provided to customers or clients. Staff entertaining (up to £150 per head per year, inclusive of VAT, for annual staff events) is allowable.

Dual-Purpose Items

A phone used for both business and personal calls cannot be deducted in full under the accruals method — only the business proportion. A computer used both for work and personal browsing is treated similarly. HMRC may accept a reasonable apportionment.

Clothing

A suit worn for client meetings is not a uniform — it is ordinary clothing that you could wear elsewhere. A lawyer's wig, a nurse's uniform, or a builder's high-visibility vest qualifies as deductible. Branded work wear (bearing your company logo) in a distinctive design that would not be worn socially may also qualify.

Training Costs

Training to maintain or improve skills in your current trade is deductible. Training for a new career or qualification in a different field is not. A self-employed journalist taking a photography course related to their journalism may deduct it; taking a plumbing course as a career change cannot.

Record-Keeping

For every expense claim, keep the receipt or invoice. For vehicle expenses, maintain a mileage log. For home working costs, record the method used (flat rate or proportional) and keep relevant evidence such as utility bills. HMRC can and does disallow expenses claims where adequate documentation is not provided.