Claiming Business Expenses: What You Can (And Cannot) Deduct

With the Self-Assessment deadline just over a week away, a lot of people are working through their expenses for the final time before filing. It's one of the areas where genuine confusion is most common - some people miss out on legitimate claims out of caution, while others inadvertently claim for things that don't actually qualify. Here's a clear look at how the rules actually work.

The Basic Test: Wholly and Exclusively

The core principle behind allowable business expenses is that they must be incurred wholly and exclusively for the purposes of the business. This sounds simple but causes genuine difficulty in practice, particularly for costs that serve a mixed personal and business purpose. Where an expense has a dual purpose, it generally can't be claimed at all unless a clearly identifiable business element can be separated out - which is exactly why costs like home working, vehicle use and mobile phones have their own specific rules rather than being judged purely against the general test.

Costs That Are Usually Straightforward

Some categories of expense are relatively clear-cut for most self-employed people and small businesses: stock and materials used directly in the business, business insurance, professional fees such as accountancy costs, advertising and marketing costs, and equipment or software used genuinely and exclusively for business purposes. Keeping proper receipts and records for these throughout the year, rather than trying to reconstruct them at the point of filing, makes claiming them both easier and more defensible if HMRC ever asks a question.

Working From Home

If you work from home, you can claim a proportion of household costs relating to the business use of your home, either using HMRC's simplified flat rate based on hours worked from home each month, or by calculating an actual proportion of costs like heating, electricity and council tax based on the space and time genuinely used for business purposes. The simplified method is easier to apply and defend, while the actual cost method can produce a higher claim for those working from home extensively, but requires more detailed record-keeping to support the figures used.

Vehicles and Travel

Business mileage can be claimed either using HMRC's simplified mileage rates, applied per business mile driven in your own vehicle, or by claiming actual costs and capital allowances if you use the actual cost method for your vehicle overall - the two approaches can't generally be mixed for the same vehicle. Ordinary commuting between home and a regular place of work generally doesn't qualify as a business expense, which surprises some people, while travel to temporary workplaces or client sites genuinely does. Getting this distinction right, particularly for anyone with a base of operations they travel to and from regularly, is one of the more commonly misunderstood areas.

Entertaining Is Usually Not Allowable

One of the most persistent misconceptions is that client entertaining - meals, drinks, hospitality - can be claimed as a business expense. In almost all cases, it cannot, for tax purposes, even though it's a genuine and often necessary cost of doing business. Staff entertaining is treated differently and can qualify for specific exemptions, such as the annual function exemption covered elsewhere, but client entertaining specifically remains one of the clearest examples of a cost that feels like it should be deductible but generally isn't.

Capital Items Are Treated Differently

Larger purchases, such as equipment, machinery or vehicles that will be used in the business over several years, are generally treated as capital expenditure rather than a simple revenue expense, with relief given through capital allowances rather than a straightforward deduction against profit in the year of purchase. The Annual Investment Allowance allows many businesses to deduct the full cost of most qualifying capital items in the year of purchase up to a generous annual limit, but it's worth understanding this distinction rather than assuming every business cost is treated the same way for tax purposes.

When in Doubt, Ask Rather Than Guess

Given how much genuine nuance exists in this area - dual-purpose costs, the distinction between capital and revenue expenditure, and specific rules for things like vehicles and home working - it's far better to ask a specific question about an expense you're unsure of than to either over-claim, risking a query or penalty later, or under-claim, simply paying more tax than you needed to out of excessive caution. If you'd like a proper review of your expenses before you file, we're happy to go through them with you.