Self Assessment Calculators
Free, accurate tax calculators for UK self-employed people. Whether you're figuring out which expense method saves you more, checking if Making Tax Digital applies to you, or working out the tax on a company car — these tools give you instant answers with no sign-up required.
Available Calculators
Which Calculator Do I Need?
Not sure which tool to use? Here's a quick guide to each calculator and when it's useful:
Trading Allowance vs Expenses Calculator
If you're self-employed or a sole trader, you can either claim the £1,000 trading allowance (a flat deduction regardless of your actual costs) or deduct your actual business expenses. This calculator compares both methods side by side and tells you which one results in less tax due. It's most useful when you're preparing your Self Assessment and deciding which deduction method to use.
Read our full guide to the trading allowance vs expenses
MTD Qualifying Income Calculator
Making Tax Digital for Income Tax is being phased in from April 2026, starting with people whose qualifying income (self-employment plus property income) exceeds £50,000. This calculator takes all your income sources, filters to qualifying income only, and tells you whether you're mandated to use MTD, from when, and whether you can volunteer early. It's essential if you're unsure whether the new rules apply to you.
Read our full guide to MTD qualifying income thresholds
Benefit in Kind (P11D) Tax Calculator
If your employer provides benefits like a company car, private medical insurance, or a low-interest loan, you owe tax on the "cash equivalent" of those benefits. This calculator handles all three benefit types, using current HMRC BIK rates and official interest rates. It's useful when you receive a P11D from your employer and need to know how much extra tax to budget for.
Are These Calculators Accurate?
All calculators use current HMRC rates and thresholds. The trading allowance calculator uses the fixed £1,000 allowance. The MTD calculator uses the phased thresholds (£50,000 from April 2026, £30,000 from April 2027, £20,000 from April 2028). The benefit in kind calculator uses official BIK rate tables for 2024-25 and 2025-26, including the diesel supplement and hybrid range bands.
These tools are for guidance only and don't constitute professional tax advice. Always verify against gov.uk or consult a qualified accountant if you're unsure.