What is a P6 tax code notice from HMRC?

A P6 turns up in your HMRC inbox, names one of your employees, and gives a tax code you have not seen before. Here is what it is, what you are supposed to do with it, and how much trouble it causes if it sits there unread.

What a P6 actually is

A P6 is HMRC telling you, the employer, to change a named employee's tax code partway through the tax year. HMRC issues one when something changes on that person's record: a company car starts or stops, a second job appears, they claim a relief, or tax underpaid in an earlier year is being collected through their code.

It is an instruction, not a suggestion. HMRC sees that person's whole income and you only see the slice you pay, so the code they give you is the one you run.

P6 or P9, the quick difference

Same idea, different timing. A P6 is mid-year and individual. A P9 is the new-year version, issued before 6 April: the P9X sets out the general changes that apply across the board, and individual P9T notices cover named employees. P9 codes go in from 6 April, and anyone with no new code carries the old one forward with any week 1 or month 1 marking taken off. For the wider set of P-forms and what each tax code letter means, our UK payroll guide has the full reference.

What to do when one lands

HMRC emails an alert rather than the notice itself. The notice sits in PAYE Online, and most payroll software pulls it down automatically if the HMRC connection is switched on. From there it is a short job, and the order matters.

1. Open the notice and check the employee, the code, and the date it takes effect.
2. Check whether it is cumulative or carries a week 1 or month 1 marking.
3. Enter it on the payroll record before the next pay run, not after.
4. If the notice came with previous pay and tax figures, put those in too. Miss them and the cumulative maths will be wrong.
5. If more than one notice has arrived for the same person for the same tax year, apply the most recently issued one and keep the others on file rather than throwing them away. If you can't tell which is current, check with HMRC before the next payday.

The week 1 and month 1 bit

Most codes are cumulative, which means each pay run looks at the whole year to date and works out what should have been paid by now. A code marked W1, M1 or X is non-cumulative: it treats every pay period on its own and ignores everything that came before. HMRC uses it when the full catch-up in one go would take an uncomfortable chunk out of someone's pay.

Your employee feels the difference on payday. A cumulative code that has dropped collects the whole year's correction in the next run, while the same code on a month 1 basis just changes the deduction going forward and leaves the earlier months alone until the year is squared up.

A worked example

Sofia is an operations coordinator in Sheffield for a marine survey company based in Singapore. She starts the year on 1257L, the standard code where the full £12,570 Personal Allowance applies. In month 6 a P6 arrives moving her to 1057L, because £2,000 of her tax-free pay has been used up elsewhere. Because the new code is lower than the one she was on, HMRC will normally issue it on a month 1 basis.

At 2026/27 rates that is £2,000 more of her pay taxed at the 20% basic rate, so about £400 more tax across the year, roughly £33 a month. On a month 1 basis her deduction goes up by about £33 from month 6, with no lump catch-up for the five months already gone. HMRC usually works out the whole year when it changes a code, so the notice may carry a slightly lower number that spreads the shortfall for those months over the rest of the year instead. If HMRC did issue the code cumulatively, the month 6 payslip would carry about £200 extra in total, roughly £167 for months 1 to 5 plus that month's £33, and then settle to £33. Nothing has gone wrong. It is a mid-year code doing a full year's job.

What happens if you miss one

Nothing dramatic on the day, which is why it is easy to let slide. The employee carries on being taxed on an out-of-date code, so they either underpay and owe it later, or overpay and wait to get it back. That isn't just the employee's problem. If the old code takes too little tax, the PAYE regulations make you, the employer, liable for the tax you should have deducted, and HMRC only lets you off, so that the employee pays it instead, if it accepts you took reasonable care and the mistake was made in good faith. A notice left unread in your inbox is hard to call reasonable care. Either way, it lands on your desk as an awkward conversation and a payslip nobody can explain. The silent version is worse: if the connection between HMRC and your payroll software quietly stops working, notices pile up unseen for months. An empty inbox and a broken connection look identical from the outside.

The thing you must not do

Never change a tax code because an employee asked you to. If someone thinks their code is wrong, they take it up with HMRC themselves, and if HMRC agrees a P6 arrives and you change the code then. Anything else leaves you running a code HMRC has not authorised, with a difference nobody can reconcile at year end.

If your company is overseas and your employee is in the UK

The same notices apply. A DPNI scheme is a real PAYE scheme with its own reference, so HMRC issues coding notices against it exactly as it would for a UK employer. That is the part overseas employers tend not to expect: the setup is a one-off, but the coding notices, the RTI submissions and the pension duties carry on every month afterwards.

When we run a scheme, that is our job. We pick the notices up, apply them to the next run, and tell the employee in plain English why their take-home moved. Our DPNI fee is £157 a month per scheme, and coding notices are in it, not an extra.

Read next

• The UK payroll guide, tax codes, P45, P60, the starter checklist and RTI in one reference.
• Your tax code is wrong, how to get it fixed, the same subject from the employee's side, for when you need somewhere to point them.
• Payroll glossary, every term and abbreviation you will meet on a UK payroll.
• UK tax rates and thresholds for 2026/27, the figures behind the codes.
• Working in the UK for a company abroad, if you are the employee rather than the employer.

General guidance for UK employers and their employees, correct for the 2026/27 tax year at the time of writing. It is not personal tax advice. Figures and the setup offer are current at the date shown above. For your own situation, ask us for a fixed quote.