About WhatsUK
Free, accurate UK financial calculators - built by a CIMA-qualified analyst using official HMRC data, so every UK resident can understand their finances without hiring an accountant.
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Our Mission
WhatsUK exists to make UK tax and financial calculations genuinely accessible to every UK resident - not just those who can afford a professional accountant. The UK tax system is notoriously complicated: income tax bands, National Insurance thresholds, stamp duty rates, corporation tax marginal relief, IR35 rules, and dozens of other rules change regularly and interact in ways that even financially literate people find confusing.
Our mission is straightforward: provide free, accurate UK financial calculators that use the official rates published by HM Revenue & Customs (HMRC) for the 2026/27 tax year (6 April 2026 to 5 April 2027), explain results in plain English, and update every tool within 48 hours of official rate changes each April.
Nobody should need to pay for a simple salary calculation or a basic stamp duty estimate. Whether you're a PAYE employee trying to understand your payslip, a contractor assessing IR35 status, a landlord calculating rental yield, or a small business owner planning corporation tax - WhatsUK gives you the tools to answer those questions confidently, completely free of charge.
We do not hide results behind paywalls. We do not require email sign-ups. We do not monetise your data. Every calculation runs entirely in your browser - we never see your income figures, property values, or financial details.
Who We Are
James Hartley
Founder and Lead Financial Analyst at WhatsUKJames Hartley is a Chartered Management Accountant (CIMA) with more than eight years of experience in UK tax, payroll and compliance. He holds a BSc in Finance and Economics from the University of Manchester and spent his early career at a Big 4 accounting firm. He founded WhatsUK to build free UK financial calculators and guides verified against official HMRC sources. He holds a BSc in Finance & Economics from the University of Manchester and spent several years at a Big 4 accounting firm before founding WhatsUK.
James founded WhatsUK after years of watching people make costly financial decisions based on inaccurate or outdated calculator websites. His goal was simple: build tools that professionals would trust, but make them accessible to everyone. He personally writes every calculator methodology, verifies all rates against official HMRC sources, and authors the WhatsUK blog.
Our Standards
Every calculator on WhatsUK is built using rates and thresholds sourced directly from HMRC's official publications. We cross-reference all figures with the relevant GOV.UK legislation and worked examples before any tool goes live.
All rates are stored in a single version-controlled tax config file, which means when HMRC publishes new rates each April, every calculator on the site updates simultaneously - eliminating the risk of inconsistencies between tools. We update within 48 hours of official announcements.
We never rely on third-party summary sites or media reports for our rate data. We go directly to the source: HMRC, GOV.UK, the Bank of England, the Student Loans Company, and the Office for National Statistics.
Official Sources Only
All rates sourced directly from HMRC, ONS, and Bank of England. No third-party estimates or media figures.
Tested Against HMRC Examples
Every calculator is verified against the worked examples published on GOV.UK before going live.
Updated Within 48 Hours
When HMRC publishes new rates each April, we update all calculators within 48 hours of the announcement.
Edge Cases Documented
Scottish rates, personal allowance taper at £100,000, and marginal relief are all tested and documented.
Our Editorial Process
All content on WhatsUK - both calculators and blog articles - is written by qualified financial professionals with direct experience in UK tax and compliance. We do not publish AI-generated content or outsource writing to non-specialists.
We follow a strict editorial process to ensure accuracy. Every calculator and article is reviewed before publication and updated when official rates change. Blog posts citing statistics or rates include direct links to official government sources so readers can verify figures independently.
Our fact-checking process works as follows: all rates and thresholds are sourced from primary government publications, recorded with source citations, then cross-referenced against HMRC's own online tax calculators where available. Any discrepancy triggers a full review before publication. Read our full editorial guidelines for how we review, update, and correct content.
If an error is reported, we investigate within 24 hours and, if confirmed, correct the calculator or article and update the "last reviewed" date visible on the page. We take accuracy seriously because for YMYL (Your Money or Your Life) content, a wrong figure can have real financial consequences for users.
Authority Sources We Reference
For the full list of sources used by each calculator, see our Data Sources page. For details on how calculations are built and tested, read our Methodology page.
Contact Us
Found an error? Have a suggestion for a new calculator? We take accuracy seriously and respond to every message. James personally reviews all reports within 24 hours.