About Diligent Finance

The author

Diligent Finance is built and maintained by Emanuele Spoti. The calculators on this site reuse the same legislative-data tables and tax-rule logic that the full planner uses for whole-of-life simulations, so the numbers you see on a calculator page match what the planner would produce on the same inputs.

For questions, corrections, or to flag a calculation that looks wrong, please open an issue on the project repository or reach out via the contact details on the privacy page.

How the calculators work

Each calculator computes its result server-side from the published HMRC legislative tables for the chosen tax year, then renders an HTML page with the answer above the fold, an explanation block targeting the long-tail questions people typically search for, and a "Sources" footer linking to the primary HMRC / gov.uk pages every rate and threshold comes from.

Inputs update the result via a small JavaScript bridge (200 ms debounce, in-place DOM updates), with the URL kept in sync via history.replaceState so refresh and link-sharing preserve the current scenario. JavaScript is required for live updates; without it, the page is still fully readable and shareable via the URL.

Data and privacy

We log a small set of pageview and interaction events for analytics. See the privacy page for what's collected, how it's stored, and your options. We do not run third-party trackers or advertising scripts. The full planner, which a calculator's inputs can be handed off to, by default operates on anonymous local storage and never requires a sign-in.

Disclaimer

The calculators and the planner are educational and computational tools. The figures they produce are not financial advice. They do not account for personal circumstances such as marriage allowance, blind person's allowance, non-standard NI categories, or anything outside the inputs the calculator asks for. For decisions that affect your money, consult a qualified financial adviser.