Pay AuditWhat it can tell you
The things a payslip cannot show you on its own
A payslip shows one month, from one job, as one payroll understood it. Most of what goes wrong is invisible from inside that view — not because anyone made a mistake, but because no single payroll has the whole picture.
Two posts, one personal allowance
Every employment gets its own tax code, and each payroll applies it to the pay it knows about. Neither can see the other. Above a certain total income the personal allowance tapers away — but if both payrolls keep giving you a full one, tax goes uncollected all year and lands later through a changed code.
Where it shows up: only when both posts are looked at together, which is why the app asks for all of them.
A tax code that never settles
A normal code is cumulative: each month looks at the year so far and corrects itself. A code marked W1, M1, X or non-cumulative does not. It taxes each month in isolation, so the year can never square itself. It is normal after a job change, and not normal months later.
Where it shows up: printed on the payslip, next to the code — easy to see, easy to not know matters.
A P60 that disagrees with your payslips
The P60 is what your employer told HMRC. If your payslips do not add up to it, one of the two is wrong — usually a payslip missing from the pile, sometimes a figure that was never paid.
Where it shows up: only when a year's payslips are totted up and compared to the certificate.
The wrong pension tier
Your contribution rate is set by your whole-time equivalent pensionable pay, not by what you actually earned. Less than full time does not automatically mean a lower tier, and a tier set from the wrong figure is wrong every month until someone notices.
Where it shows up: the percentage is printed on the payslip — the question is whether it is the right one.
Pay progression that stopped
Pay points advance with service, and on some contracts only after a meeting that has to actually happen. If it did not, nothing on your payslip will say so. It simply keeps paying the old point.
Where it shows up: by comparing your NHS service against the scale, which no payslip does.
Backdated pay taxed in one lump
Arrears and pay awards are taxed in the month they are paid, not the months they relate to. That makes one month look badly wrong when it is entirely correct — and makes a genuinely wrong month easy to dismiss.
Where it shows up: as a spike the app can name, so you know which it is.
And the ordinary checks
Every line, against the rule that produced it
Pay
Basic against the circular for your grade and pay point, plus additional rostered hours, night enhancement, weekend frequency, on-call availability, banding, London weighting and programmed activities.
Deductions
Income tax rebuilt from your tax code on a cumulative basis, National Insurance, the pension tier, and student or postgraduate loan repayments.
See what yours says
One payslip is enough to start. Free, and nothing leaves your device.