Editorial Policy

Casvia publishes UK financial calculators and plain-English guides. This page explains how we decide what to publish, where our numbers come from, how we review content and how we keep the site trustworthy.

Our content goals

Casvia exists to make UK money decisions easier to understand. Everything we publish is judged against four questions:

Is it useful? Does it help someone answer a real money question — a tax bill, a mortgage payment, a savings target?
Is it accurate? Do the rates, thresholds, allowances and formulas reflect published UK rules for the stated tax year?
Is it transparent? Can a reader see where a number came from and how it was calculated?
Is it educational? Does it inform rather than sell? We do not recommend products, predict returns or give personal advice.

Source priority

UK tax, benefit and financial rules are set by public bodies, so we treat official sources as primary. Our priority order is:

Official UK government and public bodies — GOV.UK, HMRC, ONS, Bank of England, Scottish Government and Welsh Government.
Regulators and statutory guidance — FCA guidance, MoneyHelper consumer guidance, and similar public consumer-facing bodies.
Established reference material — only where it restates official rules, never as a substitute for them.

We do not use blogs, forums or unverified third-party sites as primary sources for rates or thresholds. The full list of sources we use and how often we update them is on the Data Sources & Update Policy page.

How tax data is updated

UK tax thresholds, allowances and rates change by tax year and at fiscal events. Our approach:

Each tax-sensitive calculator records its applicable tax year (for example 2026/27) and its source, displayed on the page.
When the UK tax year changes (6 April), or after a Budget, Autumn Statement or official mid-year threshold change, we re-verify affected values against official sources and update them.
Where a rule has changed, affected pages are updated together — data layer, calculator logic where needed, tests and any related text — so the site never mixes old and new rules for the same tax year.
A date-stamped last verified note appears on calculator pages. See Data Sources & Update Policy for the full update schedule.

How calculators are audited

Every calculator is a small, inspectable program. Our audit process includes:

Formula review — each mathematical function is checked against its stated formula (for example the standard loan repayment formula for mortgages).
Boundary testing — inputs such as 0, negative values, very large values and invalid combinations are tested so the calculator fails gracefully.
Golden cases — known scenarios are re-computed independently and compared with the calculator's output (for example a £300,000 mortgage at 5% over 25 years).
Regression suite — an automated test suite runs on every change, and a full-site quality check scans all pages for broken links, missing metadata and structural errors.

How content is reviewed

Content on Casvia is produced and maintained through Casvia's editorial process. To reduce reliance on any single judgement, publication combines human review with rule-based checks:

Editorial review — every guide and calculator page is written or revised against a fixed structure (clear question, direct answer, worked example, assumptions, sources, disclaimer).
Rule-based verification — numbers in articles are checked against the calculators they link to, and calculator results are verified by automated golden tests and independent re-calculation.
Consistency checks — automated scans check titles, meta descriptions, canonical URLs, internal links and structured data across the site.
Tax-year discipline — any page that depends on UK rates must state the tax year it reflects and its source; pages are re-checked at tax-year boundaries.

AI-assisted content: how it works

We are open about this: parts of Casvia's content and code are drafted with the help of AI tools. This is only ever the starting point. Nothing AI-assisted is published unless it has passed all of the following:

Rule verification — every figure, rate, threshold and formula is checked against an official source or an independent calculation, not taken on trust from the drafting tool.
Editorial review — text is reviewed for clarity, tone, factual claims and YMYL (Your Money or Your Life) sensitivity before publication.
Technical review — calculator code is tested (unit tests, golden cases, boundary tests) and scanned before it reaches the site.
Source labelling — pages state their tax year and official source so claims can be traced back.

We never publish AI output that has not been verified, and we never use AI to invent experts, credentials, reviews or data sources.

Educational tools, not advice

Casvia provides educational calculators and general information. It does not provide personal financial, tax or investment advice, and nothing on this site is a recommendation to buy, sell or hold any product. Figures are estimates based on the inputs you enter and the assumptions shown. For decisions about your own money, check the relevant official guidance and, where appropriate, consult a regulated professional.

If you believe something on the site is wrong, please tell us — see our Corrections Policy for how we handle error reports.