Understanding allowable business expenses for limited companies is one of the most practical things a director can do to manage their tax bill efficiently. Yet it’s also one of the areas where we see the most confusion — and the most unnecessary overpayment.

The principle is straightforward: expenses that are incurred wholly and exclusively for the purposes of your business can be deducted from your company’s profits before Corporation Tax is calculated. That means a valid expense doesn’t just reduce your costs — it actively reduces the profit HMRC taxes. At the current Corporation Tax rate, every £1,000 in legitimate expenses you claim could save your company £190 to £250 in tax, depending on your profit band.

What makes this complicated in practice is that the rules have nuance. Some costs are fully deductible, some are partially deductible, some need to be processed in a specific way, and some that feel like business expenses simply aren’t. Let’s work through the areas that matter most.

HMRC’s test for whether an expense is allowable centres on purpose. The cost must be incurred wholly and exclusively for the purposes of your trade. This phrase does a lot of work.

If an expense has a dual purpose — personal and business — HMRC will generally disallow the entire cost unless it can be cleanly apportioned. That’s why, for example, a mobile phone contract that you also use for personal calls needs careful handling: a company-provided phone used for business is fine, but reimbursing a director’s personal contract in full tends to attract scrutiny.

The good news is that the range of costs that pass this test is wide. We work with limited company directors across sectors, and in almost every case there are legitimate expenses being missed simply because the director assumed the rules were more restrictive than they are.

It’s also worth being clear about what “allowable” means in practice. Claiming an expense doesn’t mean HMRC pays for it — it means the cost comes out of your profits before tax is calculated. The tax saving is a percentage of the expense, not the expense itself. Anyone promising to “make expenses tax-free” is either oversimplifying or misrepresenting how the system works.

Most allowable expenses for limited companies fall into a handful of broad categories. Here’s how we typically think about them:

Staff and payroll costs

Salaries, employer National Insurance contributions, and pension contributions are all deductible. This includes the director’s own salary paid through the payroll. The Employment Allowance — which offsets up to £10,500 of employer NI in 2026/27 — is worth checking eligibility for, as it can represent a meaningful reduction in your overall employment costs.

Travel and subsistence

Business travel is deductible: mileage (at HMRC’s approved rates if using a personal vehicle), public transport, parking, and accommodation for overnight business trips. Subsistence — meals and drinks during business travel — is deductible within reason. The key word is “business travel.” The commute from home to your regular place of work is not claimable.

Office and premises

Rent, business rates, utilities, and office supplies are all straightforward deductions. If you work from home as a director, you can charge the company a nominal rent — but this needs to be handled correctly to avoid creating taxable income in your personal hands or a benefit-in-kind issue.

Technology and software

Hardware, software subscriptions, broadband, and phone costs used for the business are all deductible. Cloud accounting software, project management tools, and professional platforms used in the running of the business are generally fine.

Professional fees

Accountancy fees, legal costs directly related to the business, and other professional services are deductible. Personal legal matters or advice related to the director’s personal affairs are not.

Beyond the headline categories, there are expenses that come up repeatedly in our work with directors that often go unclaimed — or are claimed incorrectly.

Training and CPD. Costs for professional development that relates to your existing trade are deductible. A software contractor paying for a relevant certification, or a consultant attending an industry conference, can put those costs through the company. Where it gets complicated is training for a new skill that takes you into a completely different trade — HMRC draws a distinction here.

Marketing and advertising. Website costs, digital advertising, content production, and PR are all deductible. If you’re running paid campaigns or paying a freelance designer, those costs go through the company cleanly.

Bank charges and interest. Business bank account fees and interest on business borrowing are deductible costs. Some directors forget to include these when reviewing company expenses.

Subscriptions and memberships. Subscriptions to professional bodies, trade associations, or industry publications relevant to the business are generally deductible. Personal gym memberships or social clubs are not.

Protective clothing and specialist equipment. Relevant in trades and construction especially — clothing required specifically for work (not just smart workwear) and specialist equipment are deductible running costs.

The pattern we see is that directors are often conservative by default, which might feel cautious but actually results in a higher tax bill than necessary. Checking what you’re missing costs nothing.

Not every business cost is treated as a revenue expense. Capital expenditure — spending on assets the company will use over several years — follows different rules under what’s known as capital allowances.

The most commonly used mechanism is the Annual Investment Allowance (AIA), which allows companies to deduct the full cost of qualifying plant and machinery in the year of purchase, up to the current AIA limit (£1 million as of the current tax year). This covers a wide range of assets: computer equipment, machinery, vans, office furniture, and more.

Cars are handled differently. Unlike vans, cars don’t qualify for AIA and are instead written down at either 18% or 6% per year depending on their CO2 emissions. Electric vehicles currently attract 100% first-year allowances, which makes them worth considering from a tax planning perspective if a company vehicle is on the agenda.

The distinction between capital and revenue spending matters because it affects which year the tax relief falls in. If you buy equipment outright, AIA means you can front-load the relief. If you lease rather than buy, the lease payments are typically treated as a revenue expense, spreading the deduction over the lease term instead.

We’d always recommend thinking about the timing of significant capital purchases with your accountant — sometimes shifting a purchase by a few weeks either side of the company’s year-end changes the tax picture meaningfully.

It’s worth being equally clear about what isn’t allowable, because putting non-deductible costs through the company doesn’t make them disappear — it usually creates a different tax problem.

Client entertainment is the classic example. Taking a client out for dinner feels like a business cost, and it is — but HMRC specifically disallows business entertainment as a deductible expense. You can still pay for it through the company, but it won’t reduce your Corporation Tax bill and, depending on how it’s processed, could trigger a benefit-in-kind charge.

Personal expenses put through the company — whether that’s clothing you’ll wear socially, a holiday framed as a “research trip,” or home improvements coded as office costs — create a director’s loan account problem. If those costs aren’t properly documented as a salary or dividend, they’re treated as a loan from the company to the director, which carries its own tax consequences if not repaid within nine months of the company’s year-end.

Fines and penalties are also not deductible — including HMRC late filing penalties. That’s deliberate; the tax system doesn’t subsidise non-compliance.

Our view is that the goal isn’t to push every cost through the company — it’s to make sure every legitimate cost is claimed, processed correctly, and documented well enough to withstand a review. That’s where working with an accountant who understands the detail genuinely pays for itself.