What is Allowable expenses?
Business costs you can deduct from income before your tax is worked out.
You pay tax on profit, not on turnover. Allowable expenses are the costs you can take off your income to get to that profit, so every one you fail to record is money you get taxed on unnecessarily.
GOV.UK groups them as office costs, travel, uniforms, staff, stock and raw materials, financial costs, premises, advertising, and training related to your existing business.
The test underneath all of it is that the cost must be wholly and exclusively for the business. That is stricter than people expect: a uniform counts, ordinary clothes worn to meet clients do not, and a phone used for both is claimed as a business proportion you can justify.
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