What is Self Assessment?
The process of filing your own tax return with HMRC, typically required for self-employed people and those with complex tax affairs.
Key Facts
- ✓ Required for self-employed, high earners, and those with untaxed income
- ✓ Online filing deadline: 31 January
- ✓ Paper filing deadline: 31 October
- ✓ Tax payment deadline: 31 January
- ✓ Late filing penalty: automatic £100 fine
- ✓ Payments on account if bill exceeds £1,000
Explanation
Self Assessment is the system HMRC uses to collect income tax from people whose tax is not fully collected through PAYE. You must file a Self Assessment tax return if you are self-employed with income over £1,000, earn over £150,000, have untaxed income such as rental income or dividends above the allowance, need to claim certain tax reliefs, or receive the High Income Child Benefit Charge (income over £60,000). The tax return covers the tax year from 6 April to 5 April. The deadline for paper returns is 31 October; online returns must be filed by 31 January following the end of the tax year. Any tax owed must also be paid by 31 January. If your bill exceeds £1,000, you may need to make payments on account — advance payments towards next year's bill. Late filing incurs automatic penalties starting at £100.
Try the calculator: Use our free calculator to see how self assessment affects your finances.
Self-Employed Tax Calculator →Other Glossary Terms
The system HMRC uses to collect income tax and National Insurance directly from employee wages.
National InsuranceA UK tax on earnings and self-employed profits that funds the state pension, NHS, and benefits.
Personal AllowanceThe amount of income you can earn each year before paying income tax — currently £12,570.
Basic Rate (20%)The 20% income tax rate applied to taxable income between £12,571 and £50,270.
Higher Rate (40%)The 40% income tax rate applied to taxable income between £50,271 and £125,140.
Additional Rate (45%)The 45% income tax rate applied to taxable income above £125,140.
Frequently Asked Questions
What does self assessment mean?
The process of filing your own tax return with HMRC, typically required for self-employed people and those with complex tax affairs.
Why does self assessment matter?
Understanding self assessment helps you make informed financial decisions and ensure you pay the correct amount of tax. Getting it wrong could mean overpaying or underpaying HMRC, which may result in penalties or missed savings. Use our calculators to see how self assessment applies to your personal situation.
Where can I find more information about self assessment?
HMRC publishes official guidance on GOV.UK for all UK tax topics. For a quick overview, our glossary entries are written in plain English and updated each tax year. You can also use our free online calculators to model different scenarios and understand how changes to your income, deductions, or allowances affect your overall tax position.