Tax and salary

The calculators under Tax and salary work out how much of a gross figure reaches a bank account once income tax and contributions have been taken. On the English pages they follow the payroll rules of the United Kingdom. The take-home pay calculator starts from a gross salary and deducts PAYE income tax and National Insurance, then student loan repayments and pension contributions where they apply. It handles the Scottish income tax bands, a tax code typed from a payslip and the tapering of the Personal Allowance on high incomes, and shows the result per year, month, week or hour.

The second tool answers a narrower question that comes up when a job ends: how much statutory leave is still owed under the Working Time Regulations 1998, and what it is worth. The holiday pay owed on leaving covers staff on fixed days as well as those on irregular hours, and estimates the tax and National Insurance taken from the final payment.

A third tool looks further ahead. The State Pension age calculator turns a date of birth into the day State Pension age is reached under the Pensions Act 1995 timetable. It also shows when a workplace or personal pension can first be drawn and gives a rough count of National Insurance qualifying years.

A fourth tool concerns the home rather than pay. The VAT on energy-saving materials page works out the VAT saved when solar panels, a heat pump, a battery or insulation are installed in a home, what the same job would cost once the zero rate ends, and the Boiler Upgrade Scheme grant that can come off a heat pump.

• Weighing up a job offer, a pay rise or a move to or from Scotland: the take-home pay calculator.
• Handing in notice, or being let go, with holiday not yet taken: the leaving payout tool.

Every rate, band and threshold comes from the body that sets it: HMRC and GOV.UK for income tax, National Insurance and student loans, legislation.gov.uk for the Working Time Regulations, and Acas guidance for how entitlement is counted. The figures sit in one data file per country rather than in the text, so when a new tax year begins the calculation and the explanation change together. Each tool page lists its sources with links and shows the date its figures were last checked against them.

Before a page goes live, the calculator is run against reference cases. Where an official body publishes a worked example, as Acas does for holiday entitlement, the case reproduces that example; where none exists, it is worked by hand from the published rates. The methodology explains the whole process.

Every result is an estimate for information. It is not tax, financial or legal advice and does not replace a payslip. What counts is what the employer's payroll actually deducts, and any difference over the tax year is settled with HMRC afterwards.

Several things can make a real payslip differ from the estimate: other income such as a second job, rental income or savings interest; a tax code adjusted for benefits in kind or for tax owed from an earlier year; an emergency code in the first weeks of a new job; and the timing of a final payment. Each tool page has a section listing what its calculation leaves out, so a gap between the estimate and a payslip can usually be traced to one of those items.