Tax Return Calculator UK
Tax Return Calculator UK
What Is a Tax Return Calculator?
A tax return calculator helps you estimate your tax liability or refund for UK self-assessment. It calculates Income Tax and National Insurance for employed and self-employed income combined. This tax return calculator UK is ideal for self-employed individuals, contractors, freelancers and anyone submitting a self-assessment tax return.
How to Use the Tax Return Calculator
Enter your employment income, self-employed income, tax already paid, NI already paid, tax region, tax code and allowable expenses. Click Calculate Tax Return to see your total income, total tax due, and whether you owe tax or are due a refund.
How Self-Assessment Tax Is Calculated
Your total income is combined from all sources. Your Personal Allowance is deducted first. Then Income Tax is calculated on your taxable income using the appropriate tax bands. Class 4 National Insurance is calculated on self-employed profits. Tax already paid (PAYE) is deducted to determine if you owe tax or get a refund.
Tax Return Example
Example: £35,000 employed income, £15,000 self-employed income, £5,000 tax paid, £2,500 NI paid, £2,000 expenses
- Total income: £35,000 + (£15,000 - £2,000) = £48,000
- Personal Allowance: £12,570
- Taxable income: £48,000 - £12,570 = £35,430
- Income Tax due: ~£6,200
- Class 4 NI: ~£650
- Tax already paid: £5,000 + £2,500 = £7,500
- Refund due: ~£650
Who Needs to Submit a Self-Assessment Tax Return?
- Self-employed individuals with profits over £1,000
- Contractors and freelancers
- Partners in a business partnership
- People with rental income
- High earners with income over £100,000
- People with untaxed income
Class 4 National Insurance for Self-Employed
If you're self-employed, you pay Class 4 National Insurance on your profits:
- 6% on profits between £12,570 and £50,270
- 2% on profits above £50,270
Class 2 National Insurance
Class 2 NI is being reformed. From 2025/26, Class 2 NI is effectively abolished for most self-employed people, with Class 4 NI covering contributions.
Tax Return vs Tax Calculator
A tax calculator estimates tax for employees. A tax return calculator is designed for self-assessment, combining employment and self-employed income, and calculating if you owe tax or get a refund.
Common Tax Return Mistakes
- Forgetting to include all income — include employment and self-employed income.
- Not claiming allowable expenses — expenses reduce your taxable profits.
- Using the wrong tax code — affects your Personal Allowance.
- Ignoring Class 4 National Insurance — self-employed profits are subject to Class 4 NI.
- Not accounting for tax already paid — PAYE tax reduces your bill.
- Missing the deadline — self-assessment deadlines are strict.
Important: This calculator provides estimates only. Your actual tax return may differ. Always check with HMRC or a qualified accountant for exact figures.
Important Assumptions and Limitations
- Tax year: 2025/26
- Personal Allowance: £12,570 (standard)
- Class 4 NI: 6% on profits £12,570-£50,270, 2% above
- No student loan repayments are included
- No other income sources (dividends, savings, rental) are included
- Results are estimates, not official HMRC calculations
Frequently Asked Questions
For general tax calculations, visit our Tax Calculator UK or Income Tax Calculator UK. For salary planning, try our Salary Calculator UK.