Self Assessment

When You Need to File a Self-Assessment Return

Self-assessment is the system HMRC uses to collect income tax from people whose tax is not fully collected through PAYE. You must register and file a return if you are self-employed with income over £1,000, earn over £150,000, have rental income, receive foreign income, or need to claim certain tax reliefs.

The key deadlines are: 5 October to register for self-assessment (for the first time), 31 October for paper returns, and 31 January for online returns and payment. Late filing incurs an automatic £100 penalty, with further penalties for continued delays.

You can file your self-assessment return through HMRC online services or through an accountant. Payments on account (advance payments towards next year’s bill) are due on 31 January and 31 July.

How Self Assessment Works in Practice

Self-assessment is the process of reporting your income to HMRC and calculating your tax liability. You must file a self-assessment return if you are self-employed, earn over £150,000, have untaxed income (rental, investment), or receive income from overseas. The deadline for online returns is 31 January following the end of the tax year.

Practical Tips

If you need to file self-assessment, register with HMRC as soon as possible — late registration can lead to penalties. Keep records of all income and expenses throughout the year. The tax is typically paid in two instalments: 31 January and 31 July. Payments on account (advance payments based on the previous year's liability) can catch people out — budget accordingly. Free software like HMRC's own tools can help file simple returns.

Related Topics

Common self-assessment triggers include receiving rental income, being a company director, having capital gains, or earning over £60,000 with child benefit. Many PAYE employees do not realise they need to file until HMRC contacts them. See rental income calculator for landlord tax calculations.