Methodology

IsMyPayRight uses HMRC-based rules and published rates for income tax, employee National Insurance, student loans, and core allowance logic.

The calculator runs annualised take-home calculations and then derives frequency views such as monthly and weekly. The payslip checker compares the figures you enter against an HMRC-based estimate for the selected tax year.

Salary sacrifice is modelled directly inside the calculator. Holiday buy is estimated from extra days, and EV salary sacrifice uses the monthly gross amount with a simple EV benefit-in-kind estimate rather than full list-price modelling.

Results are designed to be useful and transparent, but they are still estimates and may differ from a real payroll outcome where employer setup, pay timing, or provider rules vary.