Enter what your payslip says and see what it should have paid, worked out from your gross pay and tax code, with the reasons a real payslip diverges.
Enter your gross pay, tax code and what the payslip actually paid, and this works out what it should have paid and what could account for any gap. It also flags a tax code worth querying even when the arithmetic is right — the example below is a payslip that is correct to the penny and still costs its reader £2,514 a year. It does not prove a payslip error, and it cannot see your employer's payroll or your HMRC record: it narrows what to ask about. Everything you type is compared locally in your browser.
| Tax/source year | 2026/27 |
|---|---|
| Region | England/Wales/Northern Ireland |
| Tax code basis | 1257L where the page uses PAYE defaults |
| Pension basis | No pension deduction unless this example says otherwise |
| Student loan basis | No student loan unless selected in this example |
| Gross pay | Employment pay before PAYE deductions and pension or loan settings. |
|---|---|
| Income Tax | Tax estimated from the selected tax-year, region, tax code and taxable-pay assumptions. |
| National Insurance | Employee NI is calculated separately from Income Tax and may not follow the same bands. |
| Pension and loans | Pension method and student-loan plan can change take-home pay and payslip comparisons. |
| Pension contribution | Changing the rate or method can change taxable income, National Insurance and take-home pay. |
|---|---|
| Tax code and region | Scottish Income Tax, Welsh codes, emergency tax or a non-standard tax code can move the result. |
| Student loan plan | A different plan can change deductions because each plan uses its own threshold and repayment rate. |
| Bonus, overtime or second job | Extra pay and payroll timing can make a real payslip differ from the smooth annual estimate. |
| Tax code | HMRC tax-code changes, K codes, BR/D codes, or emergency markers can change PAYE deductions. |
|---|---|
| Cumulative basis | Week 1, Month 1 or non-cumulative payroll can differ from a smooth annual calculator estimate. |
| Pension method | Relief at source, net pay and salary sacrifice can affect taxable pay and take-home pay differently. |
| Payroll timing | Bonus, overtime, arrears, refunds, cut-off dates and corrections can all move a single payslip. |
| Why is the tax on my payslip higher than expected? | payslip difference |
|---|---|
| What do the main payslip lines mean? | payslip explainer |
| What tax code should I use for modelling? | tax code |
| How much does pension reduce take-home pay? | pension comparison |
| How does this affect a monthly budget? | budget planning |
| What is not decided here | PayBreakdown does not decide payroll correctness, lender approval, benefit entitlement or employer compliance, and does not give regulated financial, mortgage, debt, tax, payroll or legal advice. |
|---|
Both payslips below are £3,000 a month. Neither has been miscalculated. Both are exactly what their own tax code produces, and one of them is costing its reader £2,514 a year.
The first is on 1257L and pays £2,453.30. The tool reports a match and offers no reasons at all. A payslip that is right should be told it is right, and most checkers cannot bring themselves to say it.
The second is on 0T M1 and pays £2,243.80. Compare it against what 0T M1 should pay and the difference is £0.00 — payroll has done exactly what the code told it to. The problem is the code. 0T gives no tax-free allowance at all, so £209.50 a month more tax comes out than on a standard code, and the M1 marker says it is being operated without year-to-date figures — the state a payroll lands in after a job change or a missing P45.
This is the case a checker that only compares two numbers gets wrong. It would find no discrepancy and say everything is fine. This one still raises the code, because a W1, M1, X or 0T marker is evidence in its own right whatever the arithmetic says.
| Line | Correct payslip | Emergency basis |
|---|---|---|
| Tax code | 1257L | 0T M1 |
| Gross pay a month | £3,000 | £3,000 |
| Take-home it should pay | £2,453.30 | £2,243.80 |
| Take-home it paid | £2,453.30 | £2,243.80 |
| Difference from its own code | £0.00 | £0.00 |
| Cost against a standard code, a year | £0 | £2,514 |
| Reasons offered | 0 | 2 |
Your gross pay for one period is multiplied up to a year, run through the same tax engine the salary calculator uses, and divided back down. That is where the estimate comes from.
This estimate annualises one pay period, so it assumes your pay is the same every period. If you have had a rise, a bonus, arrears or a refund this year, some or all of this difference may be that rather than an error.
So the estimate is at its weakest exactly when a payslip looks most surprising, and the tool says so beside every result rather than presenting every comparison as equally solid. The one case that runs the other way is a W1, M1 or X code: payroll really does tax each period on its own then, which is what this method does, so those comparisons are directly comparable.
Enter what your payslip says and it works out what that gross pay and tax code should have produced, then lists what could account for any difference. It runs in your browser and it does not decide whether a payslip is correct.
This is not your employer's payroll and it is not your HMRC record. It sees the figures you type and nothing else, so there are things it cannot know however carefully you fill it in.
It cannot see your year-to-date totals, the code HMRC actually issued, a benefit in kind, a second job, a previous underpayment being collected, or a correction landing this month for something that happened last month. Any of those can explain a difference entirely.
It cannot reconstruct HMRC records, year-to-date payroll, P60/P45 refund positions, employer benefits or payroll-specific deductions.
Everything you type stays in your browser. The comparison runs on this page, and no payslip figure, tax code, salary or employer detail is sent anywhere, stored or recorded. You can check that yourself: open your browser's network tab and fill the form in — entering a payslip produces no request at all.
There are no ads on this page. A page that asks for your pay details is not a page to sell advertising against.
Change any figure above and the result moves with it. A payslip can differ from any calculator because payroll works pay period by pay period, so a tax-code change, a bonus, arrears or a refund can land in one month and not the next. See how each deduction is worked out.
It is a limited check, not a full payroll audit. It works out what your gross pay and tax code should have produced for one pay period and lists what could account for a difference. It does not decide whether HMRC, payroll or an employer is wrong, and it cannot see the records that would settle it.
No. The comparison runs in your browser and no payslip, salary, tax-code or deduction value is sent anywhere, stored or logged. Close the tab and the figures are gone.
No. Working out a refund needs your full P60 or P45 figures and your year-to-date pay, which this page does not ask for. Claim a refund through HMRC directly.
Last updated 2026-08-28. Checked by Sean Elsmore. Rates last checked against GOV.UK on 2026-08-07. Estimates are for planning and should be checked against official records where the decision matters.