Five payslips into 2026/27. How to read your year to date payslip figures, check the month 5 tax maths, and catch a K code before it costs you real money.
The August payslip is the most useful one of the year, and almost nobody looks at it properly. By now you have had five pay runs on the 2026/27 tax year, which is enough repetition for an error to have grown into a number worth chasing, and still enough of the year left to fix it through payroll. The place to check is your year to date payslip columns, not the tax code.
Those are the running totals down the right hand side, the ones most people scroll straight past. They are the only part of the payslip that will tell you whether the maths has actually been working.
HMRC does not run the tax year in calendar months. Month 1 runs from 6 April to 5 May, month 2 from 6 May to 5 June, and so on. That puts month 5 between 6 August and 5 September.
So if you are paid monthly, your August payslip is normally month 5, and you are exactly five twelfths of the way through the year. If you are paid weekly, you are somewhere around week 21. Those fractions are the basis for every check below.
Your payslip has two sets of numbers. One set is this period. The other set, usually headed YTD, TD, or “year to date”, is the running total since 6 April.
The four year to date payslip figures worth checking are:
The reason these matter is that PAYE is cumulative. Every pay run, payroll works out what your tax should be for the whole year so far and then deducts what you have already paid. It does not calculate each month in isolation. That is exactly why a single wrong figure in the year to date column keeps producing wrong tax, month after month, until somebody notices.
Take a warehouse team leader on £30,000, paid monthly, tax code 1257L cumulative, no pension, no student loan.
National Insurance runs per pay period rather than cumulatively. At 8 per cent on monthly earnings between £1,048 and £4,189:
So the August payslip should read roughly £12,500 gross to date, £1,452.50 tax to date, £580.80 NI to date. Two quick sanity checks you can do on any salary:
If your hours vary, as they do for most shift workers, the totals will not be this tidy. The cumulative logic still holds, though. A quiet month carries unused allowance forward, which is why a light August often produces a payslip with surprisingly little tax on it.
Look for W1, M1 or the word “non cumulative” next to your tax code. It means payroll is treating every pay period as if it were the first of the year and ignoring your year to date position entirely.
Say you started a job in June on 1257L M1 at £2,500 a month. On a non cumulative code you pay £290.50 each month, so £871.50 across June, July and August. On a proper cumulative code at month 5, with £7,500 of gross to date, your tax would be £452.50. That is £419 sitting with HMRC that should be in your account.
It reconciles eventually. But “eventually” can mean after 5 April, and £419 is worth a phone call now.
If your code starts with K, your deductions are bigger than your allowance, so instead of protecting part of your pay the code adds to your taxable pay. K247 adds £2,470 a year, which is £205.83 a month on top of your gross for tax purposes.
The usual causes are a company car, private medical cover, or tax owed from an earlier year. None of them are errors in themselves. What is worth checking is whether the benefit is still real. People carry K codes for company cars they handed back eighteen months ago.
The safeguard is the regulatory limit: PAYE cannot take more than 50 per cent of your gross pay in a single pay period, no matter how large the K number.
If you changed jobs this year and handed over a P45, your payslip should show separate lines for previous employment pay and tax, folded into the totals. If your year to date payslip figures only reflect what your current employer has paid you, the P45 never made it into payroll.
The consequence is usually underpayment rather than overpayment, and it surfaces as a bill after the tax year ends. Better to catch it in September.
There are seven monthly pay runs between September and March. That is the window in which a correction still comes back to you through your payslip instead of a P800 letter months later.
One caution on timing. Once a corrected cumulative code lands, the catch up happens in a single pay run, so the September payslip can look strange in the other direction, with unusually low tax or even a refund line. That is the system working, not a second error. Check the year to date tax figure rather than the monthly one and it will make sense.
Two deductions worth glancing at while you are in there: your pension and your student loan. Both have their own year to date columns, and both are set by your employer rather than HMRC, so a wrong student loan plan or a missing auto enrolment contribution will never show up in your tax code at all.
W1 or M1 on the code means non cumulative, and usually means you are overpaying.K code adds to your taxable pay, capped at half your gross in any pay period.If checking five columns by hand is not your idea of a good evening, the NetPay app tracks the running totals for you and flags when the tax on a payslip does not match what it should be. Free to download.
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Year to date. It is the running total of your gross pay, income tax, National Insurance, pension and student loan since 6 April, rather than the figure for that single pay period. It exists because PAYE is normally cumulative, so payroll recalculates your whole year every time it pays you.
By the August payslip you are five twelfths of the way through the tax year, so your free pay to date should be roughly £5,237, which is five twelfths of £12,570. On a steady salary with tax code 1257L, your year to date tax should be about 20 per cent of your year to date gross minus that £5,237.
It means the deductions HMRC is applying, usually benefits in kind or unpaid tax from an earlier year, are larger than your personal allowance. Instead of protecting part of your pay, the code adds an amount to your taxable pay. There is a safeguard, though, because PAYE cannot take more than half your gross pay in any single pay period.
Yes, and end of August is a good moment to do it. There are seven monthly pay runs left between September and March, so a corrected cumulative code will repay any overpayment through your payslip rather than leaving you waiting for a P800 calculation after 5 April.
Want to see your actual take-home pay?
NetPay UK works out your real net pay after tax, NI, pension and salary sacrifice, for hourly, shift and variable-income workers. Free to download.
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A note on financial advice: NetPay UK calculates take-home pay based on official HMRC tax rules. This article reflects rules in force at the time of publication (29 August 2026). Tax rules change. For complex situations, consult a qualified UK accountant or visit gov.uk/income-tax.
