What expenses can I claim on Self Assessment UK

Understanding “allowable expenses” on UK Self Assessment

If you complete a UK Self Assessment tax return, you can usually reduce the taxable profit you report by deducting certain costs you’ve incurred. These are commonly called allowable expenses. In plain English: if you paid for something in order to run your business (or to run your rental property business), and the rules allow it, you may be able to claim it and pay tax on a smaller profit.

The most important principle to understand is HMRC’s “wholly and exclusively” rule. For self-employed trading income, HMRC generally expects an expense to be incurred wholly and exclusively for the purposes of the trade to be deductible. If there’s a non-business purpose, you may need to restrict the claim (claim only the business element) or the whole cost may be disallowed, depending on the facts.

This article focuses on the most common expenses people claim on Self Assessment in the UK, especially for sole traders (self-employed) and landlords. It’s written to help you understand the categories, what usually counts, what usually doesn’t, and how to keep your claims defensible if HMRC ever asks questions. It’s not personal tax advice, and if your situation is complex (for example, you’re incorporated, you have mixed personal/business use, or you’re dealing with capital allowances or property refurbishments), getting tailored advice can be worth it.

First: what kind of Self Assessment are you doing?

Self Assessment is a filing system, not a single “type” of income. The expenses you can claim depend on what you’re reporting. Most people who ask “What expenses can I claim?” fall into one (or more) of these groups:

1) Self-employed (sole trader) or partner in a partnership: you’re reporting trading income and expenses, typically on the self-employment pages.

2) Landlord: you’re reporting property income and costs (for example, letting agent fees, repairs, insurance). The rules are similar in spirit (costs must relate to the rental business), but there are special rules in places (for example, finance costs/mortgage interest relief).

3) Employment or other income: employees can sometimes claim specific work-related expenses, but the rules and approach differ and are not the focus here.

If you have both self-employment and property income, you effectively keep two sets of “mini accounts” and claim the correct expenses against the correct income stream.

The golden rule: “wholly and exclusively” (and how mixed-use works)

For self-employed trading income, an expense is generally allowable if it’s incurred wholly and exclusively for business purposes. If a cost is partly business and partly personal (a common example is a mobile phone bill or broadband), you normally claim only the business proportion. HMRC’s manuals and guidance discuss this concept in more detail, including situations where an expense has a “dual purpose.”

In practice, what matters is whether your restriction is sensible and evidence-based. For example:

Reasonable apportionment example: You have one mobile phone you use for both work and personal calls. You review itemised bills (or usage reports) and estimate that 70% of usage is business-related. Claim 70% of the bill.

Higher-risk example: You claim 100% of your home broadband when it’s clearly used by the household for personal streaming and gaming. Unless you can justify that it’s exclusively for business, you’d usually restrict it.

When in doubt, keep your logic written down. If HMRC ever asks, being able to show how you arrived at a percentage can make a big difference.

Record keeping: the easiest way to protect your claim

Even a perfectly valid expense can become hard to defend without records. Good record keeping doesn’t need to be complicated:

• Keep digital copies (photos/scans) of receipts and invoices.

• Keep bank statements (business account if you have one).

• Keep mileage logs if you claim vehicle mileage.

• Keep notes for anything unusual (for example, why a cost was business-related, or how you split business vs personal use).

If you use accounting software, try to categorise expenses consistently (for example, “travel,” “office costs,” “professional fees”) so your Self Assessment entries are easy to produce and easy to explain.

Self-employed allowable expenses: the main categories

HMRC groups common allowable costs into categories. The exact labels you see can differ depending on whether you’re using software, a paper return, or the short/full self-employment pages, but the underlying idea is the same: you claim costs that are genuinely incurred in running the business.

Office costs (including phone and internet)

Office costs typically include the day-to-day running costs of operating your business:

• Stationery, printing, postage, packaging (if relevant to your trade).

• Business phone costs (mobile/landline) and business-only SIMs.

• Internet costs (business proportion if mixed-use).

• Computer consumables and small equipment.

• Software subscriptions that you use for the business (accounting tools, design software, project management tools).

Common pitfalls: claiming personal devices or subscriptions that are mainly for private use, or claiming a “nice to have” gadget that isn’t really used for the business.

Travel and subsistence (what usually counts)

Travel is one of the most common expense areas, and also one of the most commonly misunderstood. In general, allowable travel costs are those you incur necessarily for business journeys—for example, going to a client meeting, travelling to buy stock, or visiting a site.

Common allowable travel costs include:

• Public transport fares (train, bus, tube) for business journeys.

• Parking fees and tolls for business journeys.

• Hotel accommodation when you must stay away overnight for work.

• Reasonable food/drink costs while travelling for business (this is often called “subsistence” in everyday language), especially where an overnight stay is involved or you’re travelling outside your normal pattern.

Common pitfalls: commuting (travel from home to a normal base of work) is usually not allowable in the same way as travel to a temporary workplace. Many people accidentally claim commuting as “business travel.” If your work pattern is complex (for example, you work at one site most days), it’s worth checking the rules carefully or taking advice.

Vehicle expenses: actual costs or mileage (simplified expenses)

If you use a car or van for business, you generally have two main approaches:

1) Claim actual running costs (and restrict for personal use)

This can include fuel, insurance, repairs, servicing, MOT, and similar costs, with an adjustment for personal use where relevant. This route can be more admin-heavy because you need to track the business-use percentage.

2) Claim mileage using approved mileage rates (simplified expenses)

Many sole traders choose mileage rates because it’s simpler. HMRC’s approved mileage rates for cars and vans are commonly shown as:

• 45p per mile for the first 10,000 business miles in the tax year

• 25p per mile for each business mile over 10,000

There are also approved mileage rates for motorcycles and bicycles. HMRC publishes these rates and examples, and there are specific rules about sticking with a method for a vehicle once you start using mileage for it.

What you still need: a mileage log. It doesn’t have to be fancy, but it should show date, start/end (or at least destination), purpose, and miles.

Using your home as an office (actual costs or simplified flat rate)

If you work from home, yo