If you have ever sat down to work out what you owe HMRC and felt your shoulders climb toward your ears, this post is for you.
UK tax is not actually that complicated. It is just designed for a particular reader. The Income Tax Act, the Finance Acts, HMRC's Business Income Manual, every rate and threshold sits in documents written for tax inspectors, accountants, and barristers. The system works because those people know how to navigate it. Everybody else is left to either pay someone who can, guess, or spend an evening reading gov.uk pages that cross-reference five other gov.uk pages.
Numro is the alternative I wanted when I first had to deal with self-assessment as a freelancer. A tool that calculates accurately under HMRC's 2026/27 rules, explains every number in plain English, and treats you as an intelligent adult who can make decisions if someone bothers to lay out the facts.
What Numro is
Numro calculates the things you would expect a tax calculator to calculate: income tax, National Insurance, dividend tax, capital gains, self-employment obligations, allowable expenses. It does this under the current 2026/27 rates, with the edge cases worked in. If you cross the £100k threshold and your personal allowance starts tapering away, Numro shows the effective 60% marginal rate in the band where it applies. If you have rental income stacked on top of self-employment income, Numro models the interaction properly. If you owe Payment on Account, Numro tells you what, when, and why, so January doesn't surprise you.
The other half of Numro is the AI expense classifier. You describe an expense the way you would describe it to a friend: "lunch with potential client", "train to Manchester for client meeting", "course on advanced React for work". Numro tells you which HMRC category it falls into, whether it's allowable, and what the relevant rule is. The classifier doesn't make up tax law. It draws on HMRC's actual published guidance and produces a structured answer that matches what an accountant would tell you, with the citation attached so you can verify.
What Numro is not
Numro is not a tax filing service. It will not submit your return to HMRC. There are good tools for that, and Numro is happy to point you at them when filing time comes. Numro is a comprehension tool: it helps you understand your position. The filing itself is a separate decision.
Numro is also not financial advice. The calculations are accurate and the explanations are sourced, but every taxpayer's situation has details that only a qualified accountant can advise on properly. Numro is the tool that gets you to the point where you can have a useful conversation with that accountant, or decide that you don't need one.
The principle
The product principle behind Numro is simple. A tax tool should calculate accurately and explain clearly. Not one or the other. HMRC's own calculator is accurate but explains nothing. The big tax software products explain a lot but assume you already know what you're doing. Numro is the thing in between, and the thing in between turns out to be where most people actually live.
If that resonates, you can try Numro at numro.co.uk. It is free to use. We will write more here over the coming weeks about the specific tax topics freelancers run into most often: the £100k trap, Payment on Account, MTD for ITSA, the allowable expense rules HMRC actually enforces, the difference between subsistence and entertaining.
In the meantime, if you have a tax question you have been Googling without success, write to hello@numro.co.uk. Real questions from real people are how we know what to write about next.