HMRC P800 and tax code: paid too much or too little tax?
Updated: 2026-10-21
A P800 is a letter from HMRC that shows you paid too much or too little Income Tax in the last tax year. If you paid too much, you can claim a refund online and get it in about 5 working days. If you paid too little, HMRC usually collects it through your tax code over the next 12 months.
What is this letter?
A P800 is a "tax calculation". The tax year ends on 5 April. After that, HMRC checks what you earned and what tax was taken. GOV.UK says the letters are sent between June and March of the following tax year.
You only get a P800 if you are employed or get a pension. If you are registered for Self Assessment, you will not get one, because your tax bill is adjusted instead.
Common reasons, according to GOV.UK:
- you were on the wrong tax code
- you finished one job, started another, and were paid by both in the same month
- you started getting a pension at work
- you got Employment and Support Allowance or Jobseeker's Allowance
Sometimes HMRC sends a Simple Assessment letter instead. See our guide HMRC Simple Assessment letter: what it means and what to do.
How much time do I have?
| Event | Counted from | How long | Source |
|---|---|---|---|
| P800 is sent | End of tax year (5 April) | Between June and March of the next tax year | GOV.UK |
| Refund, claimed online | Your claim | About 5 working days | GOV.UK |
| Refund, you asked for a cheque | Your request | About 6 weeks | GOV.UK |
| Refund, letter says a cheque is coming | Date on the letter | Within 14 days | GOV.UK |
| Tax you owe, taken through tax code | 6 April (start of next tax year) | Equal amounts over 12 months | GOV.UK |
| New tax code after you update your details | Your update | HMRC tells you and your employer within 15 working days | GOV.UK |
| Emergency code after starting a new job | Your start date | HMRC can take up to 35 days to update it | GOV.UK |
| You think the P800 is wrong | Date of the letter | GOV.UK gives no time limit. Contact HMRC as soon as you can and follow any date on your letter. | GOV.UK |
I paid too much: how do I get my refund?
Your P800 tells you how. Usually you can claim with the online bank transfer service, or ask for a cheque online. You need your P800 reference number and your National Insurance number. You can also claim in your personal tax account or the HMRC app, if you have a UK bank account.
If the letter says you will get a cheque, you do not need to do anything. It comes by post. If you are owed tax for more than one year, you get one cheque for the full amount.
I paid too little: how will HMRC collect it?
HMRC usually changes your tax code, so a bit more tax is taken from your pay or pension. This is spread in equal amounts over 12 months from the start of the next tax year. It happens automatically if all of these are true:
- you pay Income Tax through an employer or pension provider
- you earn enough above your Personal Allowance to cover it
- you owe less than £3,000
If HMRC cannot collect it this way, it writes to explain how to pay. You can also choose to pay early, before the next tax year starts.
How do I read my tax code?
Your tax code is on your payslip, on a "Tax Code Notice" letter, and in your online account or the HMRC app.
| Code | What it means (GOV.UK) |
|---|---|
| 1257L | The code for most people with one job or pension. The number is your tax-free pay from that job (£12,570 Personal Allowance) with the last digit replaced by a letter. |
| L | Standard Personal Allowance |
| BR | All pay from this job or pension taxed at the basic rate, usually a second job or pension |
| 0T | Allowance used up, or new employer does not have your details |
| K | Untaxed income or benefits are higher than your allowance. Employers cannot take more than half of your pre-tax pay with a K code. |
| W1, M1, X, NONCUM | Emergency tax code |
| S at the start | Scottish Income Tax rates |
| C at the start | Welsh Income Tax rates |
Emergency codes. Tax is worked out only on that week's or month's pay, as if you earned it every time. This can be wrong. It often happens in a new job. Give your new employer your P45. If you do not have one, ask your old employer, or fill in the starter checklist. If the code is still wrong after 35 days, update it yourself or contact HMRC.
I have two jobs. Why is one taxed so much?
You get a separate tax code for each job or pension. One is often coded BR, D0 or D1, so all of that pay is taxed. Check that your Personal Allowance is on the right job. If something looks wrong, update your details in the Check your Income Tax service (part of your personal tax account) or contact HMRC. GOV.UK says it is your responsibility to make sure you pay the right tax.
What do I do, step by step?
- Check the letter is real. See our guide Is this HMRC letter real? 7 checks.
- Sign in to your personal tax account or the HMRC app. Check your tax code, jobs and income.
- Compare the P800 with your payslips, P60 and P45.
- If you are owed money, claim it online or wait for the cheque.
- If you owe money, check your new tax code on your payslip, or pay early if you prefer.
- If a figure is wrong, contact HMRC. Say which amounts are wrong and what they should be.
- Keep a copy of everything.
HMRC Income Tax helpline: 0300 200 3300. From outside the UK: +44 135 535 9022. Relay UK: 18001 then 0300 200 3300. Monday to Friday, 8am to 6pm, closed on bank holidays. Have your National Insurance number ready. By post: Pay As You Earn and Self Assessment, HM Revenue and Customs, BX9 1AS.
If HMRC agrees with you, you get a new calculation. If not, HMRC explains why.
What letter should I send? (Ready-made letter)
You may want to write to HMRC to say which figures on the P800 are wrong, or that your tax code is on the wrong job. UK Help Agent can explain the letter in your language and write a reply in English.
Record what happened, or send a photo of the letter. The explanation is free. A ready letter is £4.
Is that text about a tax refund real?
Scammers copy P800 refunds. HMRC says it never sends a tax rebate notice by text. HMRC only emails about a rebate from an address ending in hmrc.gov.uk. Do not click links or give bank details. Forward texts to 60599 and emails to phishing@hmrc.gov.uk. Go to GOV.UK yourself to claim.
What if the deadline has passed?
GOV.UK does not give a time limit for saying a P800 is wrong, so contact HMRC as soon as you can. If you never got a letter but think you overpaid, GOV.UK links to its tax refund guidance. If you think you owe tax, contact HMRC Income Tax enquiries. We could not confirm what happens to an unclaimed refund, so ask HMRC.
Is it the same in England, Scotland, Wales and Northern Ireland?
P800s come from HMRC for the whole UK. Scotland has different Income Tax rates: codes start with S. Wales uses Welsh rates: codes start with C. The pages we read do not mention Northern Ireland separately.
Frequently asked questions
When do P800 letters arrive?
After the tax year ends on 5 April. GOV.UK says HMRC sends them between June and March of the following tax year.
How long does a P800 refund take?
About 5 working days if you claim online, 6 weeks if you ask for a cheque. If your letter says a cheque is coming, it should arrive within 14 days of the date on the letter.
How does HMRC collect tax I owe?
Usually by changing your tax code, in equal amounts over 12 months from the next 6 April. This works if you owe less than £3,000 and earn enough above your Personal Allowance. If not, HMRC writes to you, for example with a Simple Assessment.
What does tax code 1257L mean?
It is the code most people with one job or pension have. You get £12,570 tax-free from that job, and the L means the standard Personal Allowance.
What is an emergency tax code?
A code ending in W1, M1 or X (your payslip may say NONCUM). Tax is worked out on each payslip alone, so you may pay the wrong amount. It is usually temporary.
I got a text about a tax refund from HMRC. Is it real?
No. HMRC says it never sends a tax rebate notice by text. Do not click the link. Forward the text to 60599.
Sources
- GOV.UK: Tax overpayments and underpayments
- GOV.UK: If you're due a refund
- GOV.UK: If you owe tax
- GOV.UK: Tax codes
- GOV.UK: What your tax code means
- GOV.UK: Emergency tax codes
- GOV.UK: If you think your tax code is wrong
- GOV.UK: If you have a K in your tax code
- GOV.UK: Income Tax enquiries
- GOV.UK: Report suspicious HMRC emails, texts and calls
Checked on: 2026-10-21
This is general information, not legal advice. Rules can change. For your own case, check the sources above or ask a free adviser, for example Citizens Advice.