Self Assessment for Beginners — What You Need to Know
Last updated: 2026-04-14
What is Self Assessment?
Self Assessment is the system HMRC uses to collect Income Tax from people whose tax is not automatically deducted through PAYE. If you are self-employed, earn untaxed income, or fall into certain other categories, you will likely need to file a Self Assessment tax return each year.
Who needs to register?
You usually need to register for Self Assessment if you are self-employed and earn more than £1,000, a company director (in some cases), earn untaxed income such as rental income or savings interest above your allowance, or receive child benefit and your income exceeds £50,000.
How to register
Register online through GOV.UK. You will need a Government Gateway account. HMRC will send you a Unique Taxpayer Reference (UTR) by post, usually within 10 working days. You must register by 5 October following the end of the tax year in which you started earning.
Key deadlines
The UK tax year runs from 6 April to 5 April. Your online tax return must be filed by 31 January following the end of the tax year. You must also pay any tax owed by 31 January. If you miss the deadline, HMRC charges automatic penalties.
What records to keep
Keep records of all income and expenses related to your self-employment. This includes invoices, receipts, bank statements, and mileage logs. HMRC requires you to keep records for at least 5 years after the filing deadline.
Filing your first return
Your first tax return can feel daunting, but it is essentially a summary of your income and expenses for the year. You can file online through your HMRC account. Many people use accounting software or an accountant to help with their first return.
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What happens if I do not register?
If you should have registered but did not, HMRC can charge penalties and interest on any unpaid tax. It is better to register late than not at all.
Do I need to register if I only earn a small amount?
If your self-employed income is under £1,000, you may not need to register. This is called the trading allowance. If you earn more, you should register.
Can I file my own tax return?
Yes. Many people file their own returns, especially if their income is straightforward. HMRC provides guidance, and accounting software can help.
How much tax will I owe?
This depends on your total income and expenses. As a rough guide, many sole traders set aside 25-30% of their profits for tax and National Insurance.
Need step-by-step setup guidance?
The Sole Trader Starter Pack covers registration, records, deadlines, and bookkeeping basics.
View the Sole Trader Starter PackBased on official guidance from:
- HMRC — Self Assessment — reviewed 2026-04-01
- HMRC — Register for Self Assessment — reviewed 2026-04-01
Important
The information on this page is based on publicly available UK government guidance and is intended for general educational purposes. Rules can change, and your specific situation may differ. Always check the latest guidance on GOV.UK or speak to a qualified professional before making decisions.
Last updated: 2026-04-14