Material tax facts must be traceable to an appropriate primary source. Each tax-critical page records the source, applicable period, retrieval date, completed source-check date and next scheduled check.
Source priority
- Legislation and official instruments. The legal text takes priority where the question depends on the law itself.
- HMRC and GOV.UK. Official guidance, manuals, notices, rates, thresholds, forms and service instructions explain how rules are administered.
- Courts, tribunals and other public authorities. Used when a decision or another authority is directly relevant to the point being explained.
- Secondary material. Professional or academic commentary may help identify an issue, but it does not replace the primary source for a material tax claim.
What the tax information record means
Applicable period
The tax year or dates to which the material information applies. A page can be accurate for one period and wrong for another.
Retrieved
The date UK Tax Hero accessed a source. It is evidence of retrieval, not a claim that the source never changes.
Source checked
The date material claims were compared with the recorded primary sources as part of the UK Tax Hero publication workflow.
Next source check
The scheduled maintenance trigger. A rule change or reported error can require an earlier check.
How calculators are checked
Calculator rules are held in versioned effective-period datasets rather than copied from page text. Each calculator must document its inputs, supported territories, assumptions, exclusions, rounding and output meaning.
- Pure calculation logic is kept separate from the page interface.
- Thresholds and rates are linked to dated primary sources.
- Tests cover important boundaries, worked examples and invalid inputs.
- Where an official HMRC calculator supports a comparable case, results are compared and differences are documented.
- Estimates are labelled honestly; an annual estimate is not presented as an exact payslip calculation.
If sources conflict
We do not hide a meaningful conflict. We check whether the sources cover different dates, territories or circumstances, prefer the controlling authority, explain uncertainty that affects the answer and withhold or narrow a conclusion when the evidence does not support a broader one.