What's behind every figure

Short version: every figure verified verbatim against HMRC primary sources.

Tax software is only as good as its numbers. Every number SoleTax shows, on this site and in the app, has one job: being right.

The tax engine

The full 2026-27 system lives in the engine: Income Tax with England, Wales and Northern Ireland's bands and all six of Scotland's, the Personal Allowance and its taper, Class 4 and Class 2 National Insurance, student loan plans, payments on account including the rules that reduce them when tax is already taken at source, and CIS deductions netted the way HMRC's own framework specifies.

Every calculation is verified before it ships. Right to the half-penny, including the rounding rules HMRC writes in the taxpayer's favour.

The compliance engine

Alongside the maths sits the rulebook. Every expense category in SoleTax carries HMRC's own wording, and every answer the app gives traces back to it. When a receipt needs a judgement, the app asks you.

Stale figures can't ship

Tax figures change every April, and HMRC re-issues the self-employment guidance every December. SoleTax moves with both. Every page shows when it was last checked, here and in the app.

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.

And the promise that keeps all of this honest: every content page on this site carries the date its facts were last verified against HMRC primary sources. When HMRC changes a rule, the page changes with it. Every change is logged on the updates page.