Deadlines, allowable expenses, what to include and how to avoid HMRC penalties — everything UK sole traders need to know about self assessment.
Home › Bookkeeping Advice › Self Assessment for Sole Traders
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Key deadlines for 2025/26
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What to include in your return
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Allowable expenses for sole traders
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HMRC penalties for late filing
Who needs to file a self assessment return?
You must complete a self assessment tax return if, in the last tax year (6 April to 5 April), you were:
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A self-employed sole trader earning more than £1,000
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A partner in a business partnership
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Earning more than £100,000 in any year
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A person receiving untaxed property income
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Earning income from abroad
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A director of a limited company paying yourself dividends
💡 Not sure if you need to file?
If you’re a sole trader and you earned over £1,000 from self-employment in the tax year, you almost certainly need to file a self assessment return. When in doubt, always file — the penalties for missing a required return are worse than filing an unnecessary one.
Key self assessment deadlines for 2025/26
5 Oct 2025 Register for self assessment — if you’re new to self assessment, register by this date
31 Oct 2025 Paper return deadline — if filing by post
31 Jan 2026 Online return deadline — file your 2024/25 return and pay any tax owed by this date
31 Jul 2026 Second payment on account — if you pay tax in advance instalments
What to include in your self assessment return
As a sole trader, your self assessment return needs to include:
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Total business income — all money received from your business
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Allowable business expenses — costs you can deduct to reduce your taxable profit
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Any other income — employment, rental, interest, dividends
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Pension contributions
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Gift Aid donations
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Student loan repayments (if applicable)
Allowable expenses for sole traders
Allowable expenses reduce your taxable profit — meaning you pay less tax. Many sole traders miss out on claiming everything they’re entitled to, paying more tax than they need to.
✅ You can claim
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Office costs (stationery, software)
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Travel (fuel, public transport)
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Clothing (uniforms only)
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Staff costs
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Business premises costs
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Advertising & marketing
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Phone & internet (business %)
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Professional subscriptions
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Accountancy & bookkeeping fees
❌ You cannot claim
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Personal clothing
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Personal food & drink
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Fines & penalties
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Entertaining clients
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Personal telephone use
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Commuting costs
HMRC penalties for late filing
Missing the 31 January deadline results in automatic penalties:
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1 day late: £100 fixed penalty
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3 months late: £10 per day (up to 90 days = £900)
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6 months late: Additional £300 or 5% of tax owed (whichever is higher)
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12 months late: A further £300 or 5% of tax owed
A £100 penalty applies even if you have no tax to pay . There is genuinely no benefit to missing the deadline.
