What is a Self Assessment tax return?

Self Assessment is how HMRC collects Income Tax from people with income not taxed at source — the self-employed, landlords, those with dividend or foreign income, and higher earners. You report all income and pay the bill via the annual return.

When is the Self Assessment deadline?

The online deadline is 31 January following the end of the tax year (so 31 January 2027 for 2025/26, and 31 January 2028 for 2026/27). Payments on account are due 31 January and 31 July.

How do payments on account work?

If your previous year's bill was over £1,000, HMRC asks for two interim payments (each ~50% of the prior bill) on 31 January and 31 July, with a balancing payment the following January. Our calculator estimates the annual total to help you budget.

2026/27 Tax Year

Self Assessment Tax Calculator (UK)

Estimate the income tax and National Insurance you owe through Self Assessment for 2026/27 across all your income sources — employment, self-employment, property, dividends and more. Use our calculator to model the total and plan your payments on account.

Who Needs to File a Self Assessment?

You generally must file if you have any of the following in a tax year:

Situation	Example
Self-employed	Sole trader or partnership profit
Property income	Renting out a flat or room
Dividends > £500	Shares or company dividends
High earner	Adjusted income over £100,000
Other	Foreign income, CGT, trusts

💡 Planning tip

🔧Add all your income into the calculator to see your combined bill. If it exceeds £1,000 you'll usually make payments on account — set aside roughly half by 31 January and half by 31 July.

Reduce Your Self Assessment Bill

Pension contributions: extend your basic-rate band and cut higher-rate tax.
Allowable expenses: for self-employment and property, deduct legitimately.
Marriage Allowance & Gift Aid: both reduce taxable income.
Trading allowance: £1,000 tax-free on casual self-employed income.