A payslip contains several categories of information and most people look at one number. Errors in payroll are common and rarely reported, because nobody is checking.
Gross versus net
Gross is what you earned before anything is taken. Net is what arrives. The difference is deductions, and every deduction should be identifiable.
The deductions to verify
Income tax, calculated against a code or bracket. Tax codes are frequently wrong after a job change, and the error persists until someone notices.
Social contributions, which vary by country and are usually a fixed percentage.
Pension contributions, both yours and the employer’s. Check the employer contribution is being made – this is a common failure and it is your money.
Anything else – insurance, union dues, salary sacrifice arrangements – should correspond to something you agreed to.
The parts people miss
Year-to-date totals, which show what has accumulated. Comparing these against expectations catches errors that a single month hides.
Leave balance, where it is shown. Accrual errors are common.
And the pay period covered, particularly if you are paid for hours worked – the period should match what you worked.
What to do monthly
Two minutes. Confirm the gross matches your contract, the deductions are ones you recognise, the pension employer contribution is present, and the net matches what arrived in the account.
Why it is worth it
Payroll errors are usually correctable when caught and awkward when found years later. Overpayments are typically recoverable by the employer, which means finding them early is in your interest too.