1. Earnings
Start with the pay you were actually given
Check the pay date, pay period and gross earnings before looking at deductions. Gross pay may include basic salary, overtime, bonus, commission, back pay or other earnings. If the gross amount is wrong, every percentage-based deduction below it can also look wrong, so there is little value analysing tax before confirming the earnings line.
If your pay varies according to hours worked, GOV.UK says the payslip must show the number of hours. Employers must also show pay before and after deductions and variable deductions such as Income Tax and National Insurance.
2. PAYE tax
Check the tax code before the tax amount
A tax code helps payroll decide how Income Tax should be collected. Compare the code on the payslip with HMRC information and any recent code notice. If you have just changed jobs, also check whether W1, M1, X or NONCUM appears, because those markers indicate emergency tax treatment.
Do not compare the tax line only with a simple annual calculator and conclude payroll is wrong. PAYE can use cumulative year-to-date pay and tax, while a salary calculator usually starts from a clean annual scenario. The two calculations answer slightly different questions.
3. NI and other deductions
Separate statutory deductions from choices and adjustments
Employee National Insurance has its own thresholds and category rules. Pension contributions can use different methods, and student-loan deductions depend on plan and earnings above the relevant threshold. A payslip can also contain workplace-specific deductions such as season-ticket loans, payroll giving or other authorised items.
Treat each line separately. If Income Tax looks right but net pay still seems low, the explanation may be pension or student loan rather than tax. TaxDecod’s payslip checker is designed to make that line-by-line review easier.
4. Year to date
YTD figures tell the story across the tax year
Year-to-date pay and tax can explain why a current month is different from a simple one-month estimate. They are especially useful after a job change, bonus, code change or correction. Compare YTD figures with previous payslips so you can identify exactly when the pattern changed.
If you still think tax is wrong, GOV.UK provides a specific service for checking the tax on a payslip. Keep the payslip, tax code and relevant HMRC notices available when you investigate.