Self-Employed Tax Calculator
Estimate tax and Class 2/4 NI for self-employed income.
What is the Self-Employed Tax Calculator?
A self-employed tax calculator estimates the Income Tax and Class 4 National Insurance a sole trader owes on their annual profit (income after allowable business expenses). It works by applying the Personal Allowance and the standard basic/higher/additional Income Tax bands to your profit, exactly as for employed income, then separately calculating Class 4 NI on profit above the lower profits limit at its own rate, with a lower rate applying above the upper profits limit. To check it by hand, deduct your Personal Allowance from profit, tax the remainder across the bands, then calculate Class 4 NI on profit above the relevant threshold using the current rates published on gov.uk — Class 2 NI rules have changed in recent years, so it's worth confirming current treatment separately.
How it works
Self-employed Income Tax is calculated the same banded way as employed Income Tax — applied to your profit (income after allowable business expenses) rather than a salary. On top of Income Tax, self-employed people pay National Insurance differently from employees: Class 4 NI is calculated as a percentage of profit above a threshold, in a two-band structure similar in shape to Income Tax bands.
UK context
Self-employed National Insurance rules have been reformed in recent years — Class 2 NI (previously a flat weekly amount) has changed significantly, with many self-employed people no longer required to pay it directly while still building qualifying years for the State Pension, though the exact current rules depend on your profit level. Because rules here have genuinely changed recently, this is one area where it's especially worth checking gov.uk's current guidance rather than relying on older information.
Tips
- Keep thorough records of allowable business expenses — these reduce your taxable profit, and getting this right (not just estimating) can meaningfully change your tax bill.
- Self-employed people file via Self Assessment and pay tax in arrears, sometimes with "payments on account" for the following year — budget for this rather than being caught out by the total due.
- Consider setting aside a fixed percentage of income for tax as you earn it, since self-employed tax isn't deducted automatically like PAYE.
Frequently asked questions
How is self-employed tax different from employed tax?
Income Tax itself uses the same bands whether you're employed or self-employed, applied to your profit rather than salary. The main difference is National Insurance — self-employed people pay Class 4 (and historically Class 2) NI instead of the Class 1 NI that employees pay, calculated differently.
Do I still need to pay Class 2 National Insurance?
The rules around Class 2 NI have changed significantly in recent years, and whether it applies to you now depends on your profit level and circumstances — check current gov.uk guidance directly, since this is genuinely one of the more frequently updated areas of self-employed tax.
What expenses can I deduct before calculating tax?
Allowable business expenses (that are wholly and exclusively for the business) reduce your taxable profit before tax is calculated — the specific rules on what qualifies are detailed on gov.uk's Self Assessment guidance.
A quick note
This is a simplified estimate — it doesn't account for Scottish tax rates, student loan repayments, or your specific allowable expenses. Self-employed NI rules have changed recently, so always check current gov.uk guidance or consult an accountant.