About SoleTraderTaxCalculator.co.uk

What this site is for

Use the sole trader tax calculator to estimate the income tax, Class 4 National Insurance and take-home profit on your self-employed earnings for the 2026/27 tax year, along with a suggested monthly amount to set aside. The Self Assessment calculator, tax set-aside calculator and quarterly tax calculator break the same figures down for budgeting through the year.

Tools such as the day rate tax calculator, self-employed National Insurance calculator and take-home profit calculator answer specific questions quickly, for example "how much tax and NI is due on £40,000 of self-employed profit?" or "what should I set aside from a £350 day rate?". For formal figures, a Self Assessment return or advice on your own circumstances, check GOV.UK and HMRC or speak to a qualified accountant.

What we cover

• Income tax on trading profit — the Personal Allowance and basic (20%), higher (40%) and additional (45%) rates applied to self-employed profit, with worked examples at different profit levels.
• Class 2 and Class 4 National Insurance — how Class 4 is charged at 6% and 2% across the profit thresholds, where Class 2 still fits for those below the small-profits threshold or paying voluntarily, and how NI is collected through Self Assessment.
• Self Assessment deadlines — registering as self-employed, the 31 January online filing and payment deadline, and how to avoid late-filing and late-payment penalties.
• Payments on account — how the January and July advance payment system works, when it is triggered, and how to reduce payments on account if your profit falls.
• Allowable expenses — what sole traders can deduct (home office, mileage, equipment, professional fees), the £1,000 trading allowance, and how to record costs correctly.
• Sole trader versus limited company — how the tax treatment differs and when incorporating may or may not be worthwhile as profit grows.

Editorial approach

Every calculator and guide is written in plain British English and reviewed against current HMRC and GOV.UK guidance for the active tax year. We prioritise practical accuracy, transparent assumptions and pages that genuinely help a self-employed person take a decision, rather than pages that restate definitions without helping anyone act.

Where a result depends on estimates or assumptions, those are explained and linked to the methodology page. Our editorial standards set out how we write, review and correct content, and the sources page lists the official HMRC and GOV.UK references behind our rates. The calculators and guides are free. The site is funded by advertising and by sales of an optional Sole Trader's Tax Survival Pack; neither affects the figures we publish or the guidance we give. Nothing here is personal tax advice.

How the site is maintained

• Calculator rates and thresholds are updated when HMRC confirms the figures for each tax year.
• Content is reviewed at each Budget and whenever official guidance changes the position for sole traders.
• Pages are corrected promptly when a reader reports a figure, assumption or wording that looks wrong.
• Before a calculator change goes live, the site's automated tests, including hand-worked cases, are run against it.

Editorial ownership and contact

Editorial owner: James Whitfield. James writes and maintains the calculators and guides on this site, covering Income Tax on trading profit, Class 4 National Insurance, Self Assessment, payments on account and the sole trader versus limited company decision. Every figure is checked against current HMRC and GOV.UK guidance, and the calculators are tested against a separate reference version of the rules, as the methodology explains. James is not a regulated tax adviser or accountant, so for decisions about your own situation, consult a qualified professional.

For corrections, data-quality feedback or editorial queries, use the contact page. Please include a link to the relevant GOV.UK or HMRC page when reporting a rate discrepancy so we can verify and update quickly.

Last reviewed: 4 November 2026. Tax year: 2026/27.