Methodology

How the calculators work

Each calculator takes a small number of inputs — such as gross salary, dividend income, or a VAT amount — and applies the relevant UK tax rules to produce a clear breakdown. All calculations run entirely in your browser using TypeScript. No data is sent to any server, and nothing is stored.

Tax-year logic and configuration

Every calculator is built around a central tax-year configuration that defines the rates, thresholds, and allowances for the active tax year. This includes income tax bands, National Insurance thresholds, dividend allowances, and VAT rates. When HMRC publishes new rates, we update this configuration so all calculators stay in sync.

What assumptions are used

Each calculator lists its assumptions clearly. Common assumptions include: you are a UK resident for tax purposes, you have one source of employment income, and you receive the standard personal allowance. Where a calculator simplifies something, it says so. We do not hide complexity — we scope it.

What these calculators do not cover

These tools are designed for common, straightforward scenarios. They do not model every edge case in the UK tax system. For example, they do not currently account for Scottish income tax rates, marriage allowance transfers, blind person's allowance, benefits in kind, or self-employment (Class 2/4 NI). Employer National Insurance is also excluded.

Limitations and when to verify

These calculators use simplified models that cover common cases well but cannot account for every circumstance. Results should be treated as estimates. Verify with HMRC or a qualified adviser if your situation involves:

• Multiple income sources or employments
• Complex reliefs, pension contributions, or cross-border obligations
• Irregular income or edge cases not modelled here
• High-value decisions where accuracy is critical

Tax year currently used