Pick your trade to prefill typical figures - then edit anything to match your year.
Every £1 you don't claim costs you
Your marginal rate: income tax + Class 4 NI = on every extra £1 of profit.
The most-missed expense categories
Tick "I claim this" for anything already in your return. Set an amount to £0 if it doesn't apply.
Business mileage
55p/mile for the first 10,000, then 25p - jobs, suppliers and clients (not commuting to one regular base).
Working from home (flat rate)
HMRC's simplified rate - no receipts needed, just a note of your hours.
Deductions you're missing
costing you about in extra tax every year at your marginal rate
Nothing obvious left on the table
You're claiming every category we check. Keep logging as you go so next January is painless.
Already filed? You can still fix it
Amend a Self Assessment return up to 12 months after its filing deadline, and overpayment relief can reach back four years for clear mistakes. Start keeping the evidence now - a photo of a receipt is enough.
Estimates, not advice - expenses must be wholly and exclusively for the business. Confirm each claim on GOV.UK before your return.
An expense must be wholly and exclusively for the business. Mixed-use costs (phone, home, car) are claimed in proportion. Everyday clothing never counts, even bought for work. Training counts when it updates existing skills, not when it teaches a brand-new trade. Pre-trade costs from up to 7 years before you started are treated as day-one expenses. And you need records - a photo of a receipt in a folder, or a mileage log, is enough.
| Scenario | Missed deductions | Tax saving | |
|---|---|---|---|
Self-Employed Expenses Checker by TaxFly — free UK tax calculators