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Why expenses matter to a sole trader
Every allowable expense you can prove reduces the profit your tax is calculated on. For a sole trader that is money straight back in your pocket, so getting expenses right is one of the simplest ways to keep more of what you earn. The catch is knowing what counts, what does not, and how to record it so it stands up if HMRC ever asks.
The rule that decides everything
Almost every question about expenses comes back to one test: the cost must be incurred wholly and exclusively for the purposes of your trade. If a cost is part private, part business, you normally cannot claim the personal part. There are exceptions built into the rules, such as simplified expenses for vehicles and working from home, which exist precisely because splitting these costs is otherwise messy.
What you can usually claim
For most sole traders the everyday allowable costs include: stock and materials; tools, equipment and protective clothing; business insurance; accountancy and professional fees; bank charges on your business account; software and subscriptions used for the business; advertising, website costs and directory listings; phone and internet (the business share); business travel including fuel for business journeys, parking and train fares; and training that keeps your existing skills up to date.
What you cannot usually claim
You cannot deduct your own wages or drawings, ordinary commuting between home and a permanent workplace, everyday clothing that is not protective or branded, fines and penalties, or client entertaining and hospitality. Personal bills, groceries and holidays are not allowable just because you are self employed. Getting these wrong is a common reason HMRC queries a return.
Simplified expenses
Instead of apportioning every receipt, HMRC allows simplified flat rates for a few things. You can use a flat rate per mile for business mileage in a car or van, a flat monthly amount for working from home based on hours worked, and a flat daily rate if you live on your business premises. You choose simplified expenses per category and cannot mix a flat rate with actual costs for the same item, so decide which method gives the better result.
Recording costs properly
Keep a record of every business cost as it happens, with a receipt or invoice and a short note of what it was for. Digital copies are fine as long as they are legible and complete. If you use cash basis accounting, you record expenses when you pay them; under traditional accounting you record them when they are incurred. Whichever you use, be consistent, and keep records for at least five years after the 31 January filing deadline.
How this lowers your tax bill
Your taxable profit is income minus allowable expenses. If you are a higher earner, every hundred pounds of genuine expenses can be worth several tens of pounds in tax saved, so the effort pays for itself. Just do not invent costs to reduce the bill; inaccurate claims are what trigger investigations.
Mistakes to avoid
The usual traps are claiming the full phone or internet bill when most use is personal, treating a personal trip as business travel, deducting fines, and losing receipts. A little discipline in your bookkeeping prevents all of these. If a cost is genuinely mixed, work out a fair business percentage and apply it consistently, and note how you arrived at it.
Get found while you grow
Keeping your costs and records tidy gives you time to focus on winning customers. As your business grows, make sure people can find you: claim your Google Business Profile and list your business where customers already search, so add your business to the directory and keep your details accurate.
When to bring in an accountant
If your affairs are simple, software plus care may be enough. Once you are dealing with VAT, mixed personal and business costs, or you simply value your time, an accountant often saves more than they cost. They can confirm which of your costs are allowable and keep you compliant, which is worth more than the fee when a deadline or a query lands on your desk.