What can I claim as a self-employed expense?

When you work for yourself, you're taxed on your profit — your income minus the allowable costs of running the business. Claiming those expenses means you're not taxed on money you spent to earn it.

What counts, roughly

The test is 'wholly and exclusively for the business': a work laptop, stock, business travel, a work phone, advertising, an accountant's fee. Something part-business, part-personal (like a phone bill) — claim the business share. Your commute, everyday clothes and client entertaining don't count. Work from home, and HMRC's flat-rate 'simplified expenses' save you totting up every bill.

Worth looking into

Keeping a simple running record of costs is the difference between a guess and a return you can stand behind. The full list of what's allowable — and the home-working and mileage rates — is on gov.uk, and an accountant can settle the grey areas for your situation.

This is general information, not accounting or tax advice — an accountant or HMRC is the right source for your situation.