How we check every figure

The method behind every number on this site and in the app. Short version: primary sources, verbatim, dated, and machine-enforced.

Tax software is only as good as its facts. Here's exactly how SoleTax keeps its facts right, so you don't have to take our word for anything.

1. Primary sources only, read verbatim

Every threshold, rate, deadline and rule comes from the primary source: gov.uk guidance, HMRC manuals, or the legislation itself. Not from blogs, not from other software's help pages, not from memory. We read the source, record the exact wording verbatim in an internal register with the date we read it, and build from that record. Each feature maps to its named source: expense rules to the Self Assessment notes, mileage to HMRC's simplified expenses page, CIS to the CIS guide, payments on account to HMRC's own legal framework manual.

2. A date on every page

Every content page on this site says when its facts were last checked against gov.uk. If a page says 4 July 2026, every figure on it was read from the live source that day. When the rules change, the page changes, and so does the date. No silent staleness.

3. The annual cycle

Tax figures change every April, and the Self Assessment guidance is re-issued every December. Both dates are in our maintenance calendar: rates are re-read from the live pages each spring, and the expense rules are re-audited against the new edition each winter. We also reconcile our figures against the professional rate tables accountants use, as an independent cross-check. Where the two ever disagree, we stop and investigate before anything ships.

4. Enforced by machinery, not memory

Good intentions forget. So the review dates live in the code itself: every rates file carries a review-by date, and our automated checks fail the build if that date passes without a fresh review. A calendar reminder can be ignored. A failing build can't.

The line we build to

SoleTax gives you information: the rule as HMRC publishes it, applied to your numbers. A mileage rate, a threshold, a deadline, whether a category is claimable. What we never do is dress up a judgement as a fact. Whether something is worth doing in your situation is a decision for you or your accountant, and when a question crosses that line, SoleTax says so instead of guessing.

That's the whole method. If you ever find a figure on this site that disagrees with gov.uk, tell us at support and we'll fix it and say so.