I’ve been freelancing in the UK for a while, and I’ve always found it surprisingly difficult to get a quick, clear idea of how much to set aside each month for Income Tax + National Insurance.

Existing calculators tend to be slow, require sign-ups, have pop-ups, or hide the result behind forms. The official gov tools are accurate but not designed for speed.

So I built a very lightweight alternative:

https://selfemployedtaxcalculators.co.uk

It gives a monthly tax/NI estimate based on your annual income, using the latest HMRC thresholds for England, Wales and Northern Ireland. There’s no tracking beyond basic analytics, no cookies (other than analytics), no accounts, and the page is intentionally minimal so it loads almost instantly.

A few notes: • It’s not meant to be a replacement for an accountant — just a quick approximation tool • Works fully client-side • No frameworks, kept deliberately simple • I’m planning to add optional features like an “embed” widget and scenario comparisons • I’m interested in expanding it into a collection of practical, no-signup tools for freelancers

I’d love feedback from this community: – Is the calculation logic clear enough? – Anything confusing or missing? – Any UX issues on mobile? – Would an API version be useful?