UK Self Assessment tax calculator
Estimate annual income tax and Class 4 National Insurance for planning. It does not calculate tax already paid, a filing balance, or payments on account. For the 2026/27 tax year.
How is Self Assessment tax calculated?
Self Assessment captures income tax and Class 4 National Insurance on non-PAYE income — sole-trader profits, rental profits and dividends. For 2026/27 the personal allowance is £12,570, the basic rate (20%) runs from £12,571 to £50,270, the higher rate (40%) from £50,271 to £125,140, and the additional rate (45%) above £125,140. Class 4 NI is 6% between £12,570 and £50,270, and 2% above. Class 2 NI was abolished from April 2024; voluntary contributions remain available. The filing deadline is 31 January following the tax-year end.
Tax Year & Profile
Income & Expenses
Personal Settings
Included: standard personal allowance, income tax, Class 4 National Insurance and an optional annual student-loan planning estimate.
Not included: PAYE or CIS tax already deducted, payments on account, pension or Gift Aid relief, losses, savings allowances, property/trading allowances, child benefit charges, or personal tax-code adjustments.
Estimated annual income tax and NI
£9,211.80
A planning estimate before PAYE, CIS deductions and payments on account.
Total Income
£48,000.00
Allowable Expenses
£12,000.00
Taxable Profit
£48,000.00
Personal Allowance
£12,570.00
Income Tax
£7,086.00
Class 2 NI
£0.00
Class 4 NI
£2,125.80
Student Loan
£0.00
Income Tax and NI
£9,211.80
Effective Tax Rate
19.19%
Estimated Net Income
£38,788.20
80.8% retained
Could payments on account apply?
HMRC uses your previous Self Assessment bill and tax collected at source. This calculator cannot determine whether payments on account apply or calculate the instalments.
Read payments on account explainedTax Breakdown
Insight
Your allowable expenses of £12,000.00 reduce your taxable trading profit from £60,000.00 to £48,000.00.
Your estimated National Insurance includes Class 4 (£2,125.80) contributions on self-employed profits.
Class 2 NI is not added by default because it is voluntary for most self-employed people from April 2024 onwards.
Check any tax already paid, claims and filing figures against your records before acting.
Disclaimer: This calculator provides a general planning estimate only. It does not calculate a Self Assessment filing balance, refund, payments on account or a personalised tax position.
Need help filing or reducing surprises?
Self-assessment is more than just submitting a return. RR Accountants helps freelancers, sole traders, landlords, and business owners manage filing, expenses, tax planning, and ongoing compliance properly.
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What this calculator helps you estimate
Income Tax Estimate
See how your taxable income may translate into income tax.
National Insurance
Estimate Class 4 NIC and see where voluntary Class 2 may matter.
Payments on account
Check the separate guidance because instalments depend on prior-year information.
Planning scope
See the tax and NI estimate before tax already paid and filing adjustments.
This calculator provides a planning estimate. Check your records, tax already paid, claims and filing position before acting.
2026/27 rates this calculator is built around
- Personal allowance: £12,570.
- Income tax bands for England, Wales, and Northern Ireland: 20%, 40%, and 45%.
- Scottish taxpayers: 19%, 20%, 21%, 42%, 45% and 48% bands for non-savings, non-dividend income.
- Class 4 National Insurance: 6% between £12,570 and £50,270, then 2% above.
- Class 2 National Insurance is not added by default; voluntary Class 2 remains available.
- Dividend allowance: £500, with 2026/27 dividend rates reflected where dividend income is entered.
Checked against GOV.UK guidance on income tax rates, National Insurance rates, and dividend tax, and Scottish Income Tax, and student-loan thresholds.
Related reading and service support
Frequently Asked Questions
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