UK Self Assessment tax calculator
Estimate income tax, National Insurance, and payment on account for sole traders, landlords, contractors, and directors. 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 income, dividends, and untaxed savings. 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
Estimated Self-Assessment Tax
£11,075.25
Based on the details entered, this is your estimated total self-assessment liability.
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
£1,863.45
Total Liability
£11,075.25
Effective Tax Rate
23.07%
Estimated Net Income
£36,924.75
76.9% retained
Estimated Payment on Account
£5,537.63
If applicable, HMRC may require two advance payments of this amount towards your next tax bill. This is a simplified estimate only.
Tax 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.
Payment on account may apply. HMRC may require two advance payments of £5,537.63 towards your next year's tax bill.
For tailored filing advice and expense optimisation, speak with RR Accountants.
Disclaimer: This calculator provides general estimates for planning purposes only. Your actual self-assessment tax position may differ depending on your records, allowances, tax code, income mix, reliefs, and personal circumstances.
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.
Payment on Account
Understand whether your next tax year may include advance payments.
Profit & Deductions Context
See how expenses and other inputs affect your overall position.
This calculator is designed to provide a useful estimate for planning purposes. For tailored advice on self-assessment, expenses, filing, and tax planning, speak with RR Accountants.
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%.
- 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.
Frequently Asked Questions
Need help with self-assessment, bookkeeping, or tax planning?
RR Accountants supports sole traders, freelancers, landlords, and growing businesses with self-assessment returns, bookkeeping, VAT, payroll, year-end accounts, and ongoing financial advice.