Self Assessment Tax Returns for Tradespeople.

Self Assessment is how you tell HMRC about income that isn't taxed automatically, like profit from working for yourself. You fill in a tax return once a year, HMRC works out the tax from what you tell it, and you pay it.

If you're a sole trader earning more than £1,000 a year from your trade, you almost certainly need to do one. It's not the same as company accounts, VAT returns or monthly CIS returns.

• Tax return: the form where you tell HMRC your income and costs for the year.
• Tax year: 6 April to 5 April. The 2025 to 2026 tax year ended on 5 April 2026.
• UTR: your Unique Taxpayer Reference, the 10 digit number HMRC gives you when you register.
• Payments on account: payments in advance towards next year's tax bill, usually half each in January and July.
• Penalty: a fine for filing or paying late.
• Tax code: the code an employer uses to take tax from wages. Some Self Assessment tax can be collected through it.
• Making Tax Digital: sending HMRC updates every 3 months through software, for people over the income limit.

If you need to do a return for the first time, you must register by 5 October after the end of the tax year (tax years run 6 April to 5 April). If your self employment income is £1,000 or less, the trading allowance means you usually don't need to.

Our guide to registering with HMRC walks you through it.

For the 2025 to 2026 tax year:

• Register by 5 October 2026, if it's your first return.
• Paper returns by 31 October 2026.
• Online returns by 30 December 2026 if you want the tax collected through your tax code from a job (only for smaller amounts).
• Online returns, and paying what you owe, by 31 January 2027.
• A second payment on account may be due on 31 July 2027.

Registering late can change your return deadline, but not your payment deadline. Always check HMRC's page and any letters.

Late return: £100 straight away, even if you owe no tax. After 3 months, £10 a day, up to £900. After 6 months, and again after 12, another 5% of the tax due or £300, whichever is more.

Late payment: 5% of the unpaid tax at 30 days, 6 months and 12 months, plus interest.

If you can't pay, file on time anyway and contact HMRC straight away. Not filing just adds more penalties.

Your first January bill can include what's left for the year just gone, plus your first payment on account towards next year. A second payment may be due in July.

Payments on account don't apply to everyone, and can be reduced if this year will genuinely be lower. Reduce them too much and you pay interest.

Start with checked records:

1. Check your income against your invoices and payments.
2. Back up your costs, and take off any personal use.
3. Check your bank, cash and cards.
4. Match CIS deductions to your statements.
5. Include any other income.
6. Check any pension, Gift Aid and other claims.
7. Check the return before you send it.
8. Save the confirmation and the tax calculation.

If your self employment and property income is over the limit, yes. Making Tax Digital for Income Tax started in April 2026 for income over £50,000, dropping to £30,000 from April 2027 and £20,000 from April 2028. You send an update every 3 months and still finish the year with a final return.

It has its own penalty points system. There are no penalties for a missed quarterly update in the 2026 to 2027 tax year.