Methodology

Tax Configuration

Each tax year from 2022/23 to 2026/27 is stored in a separate typed configuration file. The default tax year is 2026/27.

Payroll Estimate

The salary engine uses annual gross pay, PAYE tax-code interpretation, regional Income Tax bands, employee National Insurance, pension treatment and student loan thresholds. Pence are used internally wherever practical.

Rounding

Money values are rounded explicitly to pence for most payroll deductions. Student loan deductions are floored to whole pounds in line with common payroll treatment.

Official Sources

Core tax data is sourced from GOV.UK Income Tax rates, HMRC rates and allowances, GOV.UK Scottish Income Tax, GOV.UK National Insurance rates, GOV.UK student loan repayment information, and GOV.UK statutory pay pages.

Assumptions Requiring Review

The 2026/27 automatic enrolment qualifying earnings band uses the established GBP 6,240 to GBP 50,270 values with an explicit configuration note because a current official DWP threshold page was not discoverable during verification.