Disclaimer

What this tool does

KnowMyTax does the maths. You enter your income; we apply HMRC's published rates and thresholds and show you the breakdown. Everything runs in your browser — nothing is sent to a server.

What this tool isn't

• Not tax advice. Calculator results are illustrative. They don't account for every relief, allowance, or quirk of your specific situation.
• Not a tax return. Numbers shown here aren't a Self Assessment submission. Use HMRC's official services to file.
• Not a Status Determination Statement. The IR35 Checker scores you against the standard case-law factors. It's not a legal status determination.
• Not legal advice. For complex situations — incorporation, mixed income, overseas elements, disputed IR35 status — talk to a qualified accountant or tax adviser.

Tax rates and accuracy

Rates and thresholds are verified against HMRC and Revenue Scotland for the tax years shown. We update each April when new rates take effect. For Custom tax year, you're entering your own rates — we make no claims about the accuracy of projected scenarios.

For details on every figure used and where it comes from, see Methodology.

Useful HMRC links

• Income Tax rates and bands
• National Insurance rates
• Corporation Tax rates
• Off-payroll working (IR35) guidance
• HMRC's CEST tool
• Scottish Income Tax rates

Limitation of liability

Use of KnowMyTax is at your own risk. We accept no liability for tax decisions made based on calculator output. When the numbers matter, verify with HMRC or a qualified adviser.