Most payslip mistakes come from a wrong tax code. Check the code first, then each deduction against the 2026/27 rates below. For a £2,500 monthly salary (£30,000 a year) with the standard 1257L code in England, you should see about £290.50 Income Tax and £116.20 National Insurance, leaving about £2,093.30 before any pension or student loan.
1. Check your tax code
Most people should have 1257L: £12,570 of tax-free pay a year, or about £1,048 a month. S1257L means Scottish rates. If you see BR, D0, 0T, a K code or an emergency code (W1, M1 or X), find out why. Our tax code calculator explains each one.
2. Check Income Tax
On a 1257L code in England, Wales or Northern Ireland, monthly tax is roughly 20% of your pay above £1,048, and 40% of anything above about £4,189. A monthly payroll uses slightly different tables than a simple yearly figure, so allow for a few pounds of difference.
3. Check National Insurance
Employees pay 8% on monthly earnings between £1,048 and £4,189, and 2% above £4,189. National Insurance is worked out on each pay period on its own, so a month with a bonus or overtime has more at 8%.
4. Check pension contributions
Under auto-enrolment you pay at least 5% (including tax relief) and your employer 3%, usually on qualifying earnings between £6,240 and £50,270 a year. With a net pay scheme, the pension is taken before tax, so your taxable pay is lower. With relief at source, you pay 80% and the provider adds 20%. With salary sacrifice, your gross pay itself is lower.
5. Check student loan repayments
| Plan | Monthly threshold | Rate |
|---|---|---|
| Plan 1 | £2,241.66 | 9% |
| Plan 2 | £2,448.75 | 9% |
| Plan 4 | £2,816.25 | 9% |
| Plan 5 | £2,083.33 | 9% |
| Postgraduate | £1,750 | 6% |
On £2,500 a month, a Plan 2 borrower repays 9% of £51.25, which is about £4.61.
6. Compare with a calculator
Put your salary, pension and student loan plan into the take-home pay calculator. If your payslip is more than a few pounds out, and it isn't a bonus month or a code change, ask your payroll team.