The Question That Trips Up Almost Every Sole Trader

You buy something. You use it partly for work. You wonder: can I put this through the business? You search online, find a list of "allowable expenses," and your specific situation isn't on it. So you either guess, skip it entirely, or spend twenty minutes going round in circles on a forum.

This post is not another list. It's a decision-making guide - a way to think through any expense, including the borderline ones, so you can reach a confident answer yourself. We'll walk through a simple three-step test and then apply it to real situations sole traders face every day: laptops, client meals, training courses, home office costs, and phones.

If you're filing your own MTD quarterly updates without an accountant, this is the thinking process you need.

First: What Does HMRC Actually Mean by "Allowable"?

HMRC allows sole traders to deduct expenses that are "wholly and exclusively" incurred for the purposes of the trade. That phrase - wholly and exclusively - is the legal standard. It sounds strict, and in some ways it is. But in practice, HMRC and the courts have interpreted it with common sense for decades.

The working definition most sole traders can use is this: an expense is allowable if it is ordinary and necessary for your specific type of business. "Ordinary" means it's the kind of cost people in your line of work typically incur. "Necessary" means it genuinely serves a business purpose - not just a convenient one.

That's the foundation of the test below.

Note: This post is aimed at sole traders. If you're a landlord, the rules on what counts as an allowable expense differ in important ways - see our guide on landlord expenses in MTD instead.

The Three-Step Test

Before you categorise any expense, ask yourself these three questions in order. If you get a "no" at any step, you've found your answer.

Step 1: Does this cost exist because of my business?

Would you have bought or paid for this if you had no business at all? If the honest answer is yes - you'd have it anyway - then it's a personal expense, even if you use it for work sometimes.

A coat you wear to client meetings is still a coat you wear everywhere else too. You'd own a coat regardless. That makes it personal. A branded uniform you wear only for work is different - you wouldn't buy it if you had no business.

Step 2: Is the business use real and specific - not vague?

It's not enough to say "I might use this for work." The business use has to be genuine and identifiable. Vague potential doesn't count.

Buying a book about your industry because it helps your work is specific. Buying a general business book because it might give you ideas someday is harder to justify - especially if it sits unread on a shelf.

Step 3: Is the amount reasonable for what it is?

HMRC doesn't set price caps on most expenses, but it does expect costs to be proportionate. A sole trader buying a £15,000 coffee machine for a home office would raise questions. The same trader buying a £400 laptop replacement wouldn't.

If the amount seems out of proportion to the business need, you'll want to document your reason for it clearly. For mixed-use items - things used for both business and personal purposes - you can often still claim the business proportion. More on that below.

What About Mixed-Use Expenses?

Plenty of real-world expenses are split between personal and business use. HMRC accepts claims for the business portion of mixed-use costs, as long as you can identify and justify that split.

The key is to use a consistent, defensible method. Time is often the simplest measure. If you use your phone for business 60% of the time, you can claim 60% of the bill. If you use a room in your home as an office, you can claim a proportion of relevant household costs.

For more on this, see our post on mixed-use expenses and claiming the business percentage.

Now Let's Apply It: Seven Real Scenarios

Scenario 1: A Laptop

You buy a new laptop for £900. You use it for client work, invoicing, and email - but also for personal browsing and streaming.

Step 1: Would you own a laptop without the business? Possibly, but this particular purchase is driven by work need. If you replaced an old machine specifically because the old one couldn't run software you need for clients, the business is the reason for the cost.

Step 2: The business use is specific - client projects, invoicing, business email. That's real and identifiable.

Step 3: £900 is a reasonable cost for a working laptop.

Conclusion: If you use it primarily for business, claim it in full. If personal use is significant, claim the business proportion. Keep a note of your reasoning.

One more thing: a laptop costing over a certain amount may need to be treated as a capital item rather than a straight expense. HMRC's capital allowances rules apply here - you may be able to claim the full cost in year one using the Annual Investment Allowance. This is worth checking if you're spending a few thousand on equipment.

Scenario 2: Client Meals

You take a client to lunch to discuss a project. The bill is £65. Can you claim it?

Step 1: You'd eat lunch anyway - but not at a restaurant, not with a client, and not as part of a business meeting. The cost above your normal lunch exists because of the business.

Step 2: The purpose is specific: a working meeting with a named client. Keep a record of who it was with and what was discussed.

Step 3: £65 for a business lunch is reasonable.

Conclusion: Generally allowable as an entertainment expense - but there's an important catch. HMRC does not allow a deduction for "business entertainment" in most cases, which includes meals with clients. Meals with employees (if you have any) are treated differently. As a sole trader entertaining clients, this cost is typically not deductible under current rules, even if it's genuinely for business.

This is one of the most common mistakes sole traders make. Meals you buy for yourself while working away from your usual place of work can be allowable - but meals for clients usually aren't.

Warning: Client entertaining - including meals, drinks, and event tickets for clients - is not an allowable deduction for sole traders under HMRC's rules, even when the meeting is genuinely for business. Don't claim these as expenses in your quarterly update. See grey-area MTD expenses for more on this.

Scenario 3: Training and Courses

You pay £300 for an online course to improve a skill you use in your business. You also pay £200 for a general productivity course you think might help you work smarter.

The £300 course: It directly develops skills you use in your trade. That's clearly ordinary and necessary for the business. Claim it.

The £200 course: This is vaguer. "Working smarter" is a personal benefit as much as a business one. If you can show a direct link to your work - for example, you're a freelance project manager and it's a project management course - it has a better chance of standing. If it's a general self-help or lifestyle productivity course, the link is too loose.

Conclusion: Training that develops existing business skills is allowable. Training that helps you enter a new trade or profession is generally not - that's capital, not revenue. A nurse taking a new specialism course to start a new practice would be in different territory from a nurse updating existing clinical skills.

Scenario 4: Home Office Costs

You work from home. Your broadband, heating, and electricity all partly support your business. Can you claim them?

Yes - but you need to identify the business proportion. The simplest approach HMRC accepts is to use the number of rooms in your home and the hours you use one room for work. You're not claiming the whole bill; you're claiming a fair share of it.

Alternatively, HMRC offers a flat-rate simplified expenses method for home working. You claim a set amount per month based on the hours you work from home each month, without calculating actual costs. This avoids the need to work out proportions.

You can check the current simplified expenses rates on GOV.UK.

Conclusion: Home office costs are allowable - but only the business proportion. You can use actual costs or the simplified flat rate. You can't claim mortgage interest as a sole trader working from home (that's a landlord rule, and even then it works differently - see landlord mortgage interest in MTD).

Scenario 5: A Mobile Phone

You use one phone for everything - personal calls, business calls, WhatsApp with clients, and scrolling social media at night.

Step 1: You'd own a phone regardless. But the line rental and calls include business use.

Step 2: The business use is real - client calls, job-related messages, work emails. It's identifiable.

Step 3: You need to estimate the business proportion honestly. If 40% of your usage is business, claim 40% of the monthly bill.

Conclusion: Claim the business proportion. If you have a dedicated business phone that's used only for work, you can claim 100% of that contract.

Scenario 6: Clothing

You're a self-employed photographer. You spend £120 on smart clothes to look professional at shoots. Can you claim it?

Step 1: Would you own smart clothes without the business? Almost certainly yes. Smart clothing is part of everyday life for most people.

Step 2: "Looking professional" is not a specific enough business purpose to override the personal use. You can wear these clothes anywhere.

Conclusion: Not allowable. This is a well-established position and it catches many sole traders out. The exception is genuinely protective clothing (hi-vis, steel-toe boots, protective overalls) or a branded uniform you'd never wear outside work.

Scenario 7: Software Subscriptions

You pay for a design tool subscription at £25 per month. You also pay for a cloud storage service at £8 per month that you use for both personal photos and business files.

The design tool: Used entirely for client work. Clearly allowable in full.

The cloud storage: Mixed use. Estimate the proportion of business files stored versus personal. Claim that proportion of the monthly cost.

Conclusion: Business-only software is fully claimable. Mixed-use software is claimable in proportion. Keep a note of how you calculated the split.

How to Record Your Decision - Not Just the Amount

When you're filing quarterly updates through MTD, you're entering income and expenses into categories. But HMRC can ask questions later, and when they do, they'll want to see that your categorisation was deliberate - not a guess.

For borderline expenses, get into the habit of keeping a brief note alongside your receipt or record. Something like:

You don't need a formal document. A note in a spreadsheet column, a label in your records folder, or a line in your bookkeeping tool is enough. The point is that you can show you made a conscious, reasoned decision - not that you just bunged it through.

For more on what records HMRC expects you to keep, see what proof HMRC needs for MTD expenses and what records sole traders must keep for MTD quarterly updates.

What Happens If You Get It Wrong?

Mistakes happen, especially when you're filing without an accountant. HMRC's compliance approach to MTD is not designed to catch honest errors made in good faith. That said, there's a difference between a mistake and a pattern of claiming obviously personal costs.

If you realise you've miscategorised something after filing, you can usually correct it. See our guide on whether to amend your MTD quarterly update after filing. For a broader look at which errors actually matter, this post on MTD filing errors is worth reading.

The more useful habit is to apply the three-step test at the point of spending, not months later when you're trying to remember what something was for.

A Quick Reference: The Three-Step Test

  1. Does this cost exist because of my business? - If you'd have it anyway with no business, it's personal.
  2. Is the business use real and specific? - Vague potential doesn't count. Identify the actual purpose.
  3. Is the amount reasonable? - Proportionate to the business need. For mixed use, claim the business share only.

Run any expense through these three questions and you'll get to the right answer most of the time. The exceptions - client entertaining, clothing, training for a new trade - are worth knowing in advance so they don't catch you out.

Note: If you're unsure about a specific expense and the amount is significant, it's worth checking the HMRC guidance on self-employed expenses directly, or asking an accountant before you file - not after. HMRC's guidance is plain and searchable by expense type.

Putting It Into Practice With MTD

When you log expenses in your MTD record-keeping, each one goes into a category: office costs, travel, stock, professional fees, and so on. Getting the category right matters for accuracy, but the bigger question is whether the item should be in your records at all.

The three-step test answers that first question. Once you've decided an expense is allowable, categorising it is usually straightforward. If you're not sure which category fits, see our post on common MTD expense miscategories.

The goal is to be able to look at every line in your expense records and say: I know why this is here, and I can explain it. That's the standard HMRC expects, and it's the standard that protects you if questions are ever asked.

Keep Your Expense Records Tidy From Day One

AffordableMTD makes it straightforward to log, categorise, and submit your expenses as part of your MTD quarterly updates - without needing accounting software designed for much larger businesses. Import your expenses by CSV, use AI-assisted categorisation to speed things up, and submit directly to HMRC.

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Summary

Most expense decisions aren't complicated once you have a framework. Ask whether the cost exists because of your business, whether the business use is real and specific, and whether the amount is proportionate. For mixed-use items, claim the business share and note how you calculated it. Know the common traps - client entertaining, everyday clothing, training for a new trade - so you don't claim things that look reasonable but aren't allowable. And keep a brief note of your reasoning alongside any borderline item. That habit alone will make your quarterly updates more accurate and give you confidence if HMRC ever asks.