I've got a letter from HMRC: what is it?

Find your letter

Some HMRC letters are known by a reference code (such as P800 or PA302). Find yours below: each entry says what it is, why you probably got it, what to do and by when, and links to our full guide. Two rules apply to all of them: the deadline printed on your letter is the one that counts, and if you are unsure a letter is real, check it before you pay or reply.

• Refund or underpayment after the tax year: P800 or Simple Assessment
• A new tax code: Tax Code Notice (P2)
• Told to send a tax return, a tax bill or a statement: Self Assessment letters
• A fine or an overdue amount: penalties and overdue tax
• HMRC asking you to check something or opening a check: checks and nudge letters
• Child Benefit, National Insurance or a refund: Child Benefit charge, National Insurance, refunds

First: is it really from HMRC?

• HMRC says you will never get an email, text, app message (such as WhatsApp) or phone call from HMRC that tells you about a tax rebate or penalty or asks for your personal or payment information (GOV.UK: report scam HMRC messages). It also says HMRC will never threaten arrest, leave a voicemail threatening legal action, or ask you to pay with gift or payment vouchers (GOV.UK: identify tax scams).
• Real letters can be about penalties and refunds. GOV.UK lists specific HMRC letters, by code, on Check if a letter you've received from HMRC is genuine. If a letter is not listed and you are unsure, GOV.UK says to contact the HMRC team the letter says it is from, for example the Self Assessment team (GOV.UK: report scam HMRC messages).
• HMRC letters may carry a QR code. HMRC says a QR code in its letters usually takes you to GOV.UK guidance and will never take you to a page where you have to enter personal information (GOV.UK).
• To report a fake: forward texts to 60599 (network charges apply), forward emails to [email protected], screenshot app messages and email them there, and send details of a fake HMRC social media account to [email protected]. Scam emails that are not about HMRC go to [email protected], and texts to 7726 (GOV.UK: avoid and report scams).

More on the common cons: how to spot and report HMRC scams.

P800 tax calculation letter

What it is

HMRC's check, after the tax year ends on 5 April, of the tax taken from your pay or pension. It says you paid too much (a refund) or too little.

Why you got it

You are employed or get a pension and, for example, were on the wrong tax code, were paid by an old and a new job in the same month, started a workplace pension, or got Employment and Support Allowance or Jobseeker's Allowance. They go out between June and March of the following tax year. If you are in Self Assessment you will not get one: your bill is adjusted instead (GOV.UK).

What to do

If it says you can claim a refund online, claim with the reference number on the letter and your National Insurance number; GOV.UK says the money arrives within 5 working days by bank transfer, or 6 weeks if you ask for a cheque. If it says a cheque will be sent, you need do nothing: it arrives within 14 days of the date on the letter (GOV.UK). If you owe, HMRC usually collects it through your tax code in equal instalments over 12 months from the start of the next tax year, where you pay tax through PAYE, earn enough above your Personal Allowance and owe less than £3,000 (GOV.UK). If a figure is wrong, tell HMRC which amounts and what they should be.

Full guide

P800 tax calculation letter explained

Simple Assessment (PA302)

What it is

A tax bill, which GOV.UK says is also known as a PA302, for Income Tax HMRC could not collect through your tax code. It sets out how much you owe, how it was worked out and how to pay (GOV.UK).

Why you got it

GOV.UK gives these reasons: you owe Income Tax that cannot be collected through your tax code, you owe £3,000 or more in tax, you need to pay tax on your State Pension, or you have untaxed income such as savings interest or dividends (GOV.UK).

What to do and by when

Check every figure against your pension, benefit and payslip records. If one is wrong, query it within 60 days of the date the notice was issued (TMA 1970 s.31AA(3)), saying which amounts are wrong and what they should be; you still have to pay by the deadline unless HMRC tells you it is delaying the payment (GOV.UK). Payment is due by 31 January after the end of the tax year, or, if the notice was given after 31 October, 3 months after it was given (TMA 1970 s.59BA(4) and (5)). Pay using the 14-character reference starting with X on the letter (GOV.UK). An overdue bill brings letter IDMS99P, which asks you to pay or call within 28 days of receiving it (GOV.UK).

Full guide

How to check and pay a Simple Assessment

Tax Code Notice (P2)

What it is

A 'Tax Code Notice' telling you your new tax code and how HMRC worked it out (GOV.UK). HMRC's own research calls it the P2 Coding Notice (HMRC).

Why you got it

GOV.UK lists, among others: a new job, taxable state benefits, a second job or pension, savings interest above your Personal Savings Allowance, a change in your State Pension, company benefits starting or stopping, claiming Marriage Allowance (codes ending M or N), job expenses, paying the High Income Child Benefit Charge, paying back the Winter Fuel Payment, or collecting tax you owe from being on the wrong code (GOV.UK).

What to do

There is no deadline, but check it now: compare the allowances and deductions with what you actually get. If something is wrong or missing, update it in the Check your Income Tax service (GOV.UK). A code can also change to collect a Self Assessment bill of less than £3,000 if you are in PAYE and filed on paper by 31 October or online by 30 December; you can ask on your return for it not to be collected this way (GOV.UK).

Full guides

How to read a PAYE coding notice; tax code explainer; how to check your tax code

Self Assessment letters

Notice to file a tax return (SA316)

A formal notice that you must send a Self Assessment return; HMRC's research calls it the SA316 notice to file (HMRC). The normal deadlines are 31 October after the tax year for a paper return and 31 January for an online one. If the notice was given after 31 October, you have 3 months from the date of the notice, paper or online; if it was given between 1 August and 31 October, a paper return is due within 3 months of the notice and an online return still by 31 January (TMA 1970 s.8(1D) to (1G)). If you need to register yourself, tell HMRC by 5 October after the tax year (GOV.UK). See Self Assessment deadlines and how to register.

Self Assessment statement and tax calculation (SA302)

After you file you get a statement (your bill: what you owe, payments on account due, payments made shown as 'CR', and any balancing payment) and a tax calculation, also known as an SA302, showing how the tax was worked out. Pay by midnight on 31 January after the tax year. If you file late or close to the deadline the statement may not arrive in time, so check your online account (GOV.UK). See how to pay your Self Assessment bill and how to get your SA302.

Payments on account

Two advance payments towards next year's bill, each normally half of last year's, due by 31 January and 31 July. You do not have to make them if last year's bill was less than £1,000 or more than 80% of your tax was paid at source, for example through your tax code. If you expect a lower bill you can ask to reduce them online or on form SA303, but you pay interest if you reduce them too far (GOV.UK). See how to reduce payments on account.

Penalty notices and overdue tax

Late filing penalties (Self Assessment), under Finance Act 2009 Schedule 55:

• £100 as soon as the return is late (para 3);
• after 3 months, £10 a day for up to 90 days, if HMRC decides to charge it and gives you notice (para 4);
• after 6 months, the greater of 5% of the tax due on the return and £300 (para 5);
• after 12 months, the greater of 5% and £300 again, or a higher percentage if you deliberately withheld information (para 6).

Late payment penalties are 5% of the tax still unpaid at 30 days, 6 months and 12 months, plus interest on the amount owed (GOV.UK; FA 2009 Sch 56 para 3). GOV.UK says to pay a penalty within 30 days of the date on the penalty notice, and you can appeal if you have a reasonable excuse. If you have joined Making Tax Digital for Income Tax, points-based late submission and new late payment penalties replace these from the tax year you join; earlier years keep the old penalties. HMRC also says that from April 2027 the new penalties will apply to everyone who submits a personal Self Assessment tax return (GOV.UK); see MTD penalty points for how they work.

Letter IDMS99 (amount overdue) says HMRC's records show a payment is overdue and explains what happens if you do not pay or call within 28 days of receiving it. GOV.UK says you must not ignore it (GOV.UK). If you cannot pay in full, ask about a payment plan.

Full guides: HMRC penalties; how to appeal an HMRC penalty; how to set up Time to Pay; MTD penalty points.

Checks, enquiries and nudge letters

Letters asking you to check your tax ('nudge' letters)

'Nudge letter' is an informal name, not an HMRC code. These letters say HMRC's records suggest something may be wrong or missing and ask you to look. In one past example GOV.UK listed, letters sent to companies between April and September 2026 about Corporation Tax Marginal Relief, HMRC asked them to check their returns, correct any errors and make a disclosure, or say why the returns were right, and said that if they did not respond it might take further action, including opening a compliance check (GOV.UK). Do what the letter asks by its deadline. See responding to a nudge letter and voluntary disclosure routes.

Compliance check or notice of enquiry

If HMRC starts a compliance check it asks you to read factsheet CC/FS1a, which explains that HMRC may ask for information or documents, ask for a meeting (which you can choose whether to have) or ask to visit business premises, and that you cannot ignore a formal information or inspection notice (HMRC CC/FS1a). A formal enquiry into a Self Assessment return is a notice of enquiry under section 9A of the Taxes Management Act 1970. For a return filed on time, HMRC must give it within 12 months of the day the return was delivered; for a late or amended return, by the quarter day (31 January, 30 April, 31 July or 31 October) after the first anniversary of filing or amending (TMA 1970 s.9A(2)). See HMRC tax investigations and getting through an HMRC enquiry.

High Income Child Benefit Charge

HMRC writes about this charge through a new tax code if you pay it through PAYE, or with a letter telling you what to do next after you register for Self Assessment (GOV.UK). The charge applies, for example, if you or your partner gets Child Benefit and one of you has adjusted net income over £60,000; the higher earner pays. For 2026/27 it is 1% of the Child Benefit for every £200 over £60,000, and all of it over £80,000. You can pay through PAYE only if you do not need a tax return for another reason, you are paying for the current or previous tax year, and it is on or before 31 January after the tax year you are paying for; otherwise you pay through Self Assessment, and if you do not already send a return you must tell HMRC by 5 October after the tax year (GOV.UK). See the High Income Child Benefit Charge, the HICBC calculator and paying it through your tax code.

National Insurance letters

GOV.UK lists these genuine HMRC letters (GOV.UK):

• CA4361: HMRC thinks you may have paid too much National Insurance and asks about your past employment, online or on the paper form, before confirming any refund.
• NISPAR1MM: your record shows you kept paying National Insurance after State Pension age; HMRC may invite you to claim a refund.
• LCL2REG2MM: you declared self-employed or partnership income for a year from 2015 to 2016 to 2023 to 2024 but did not register for Class 2, you are at or within 2 years of State Pension age, and those years are not qualifying years. It asks you to contact the Department for Work and Pensions before deciding whether to pay.
• CA2490: you may be missing Home Responsibilities Protection for 1978 to 2010, for example if you got Child Benefit for a child under 16.

If you find gaps in your record, voluntary contributions can normally be paid only for the past 6 years, with a deadline of 5 April each year (GOV.UK). Check your State Pension forecast first, then see voluntary National Insurance and how to claim a National Insurance refund.

Refund letters and repayment cheques

• A P800 tells you either to claim the refund (online, in your personal tax account or the HMRC app) or that a cheque is on its way automatically (GOV.UK).
• OCA300 says student loan deductions are being repaid and asks for personal information to speed up the repayment. GOV.UK suggests calling the Income Tax general enquiries helpline to confirm the request is genuine (GOV.UK). See student loan overpayment refunds.
• A Self Assessment repayment claim can bring a letter asking for more information. GOV.UK says any request to send information to an email address that does not end in 'hmrc.gov.uk' is not genuine. A separate letter, sent when HMRC thinks you do not meet the criteria for a Self Assessment return, gives you 30 days to call if you disagree; otherwise HMRC will not process the return, make the repayment or send you a notice to file a return in future (GOV.UK).

See how to get a tax refund.

If you disagree with a decision

A decision letter tells you how to appeal and by when. For direct taxes such as Income Tax the deadline is usually 30 days from the date of the letter, and for a penalty usually 30 days from the date it was issued; if you miss it, you will need to give a reason. If HMRC does not change the decision you are offered a review, and you have 30 days from the date of that offer to accept it or appeal to the tax tribunal (GOV.UK). For a Simple Assessment you first query it within 60 days, then have 30 days from HMRC's decision letter to appeal (GOV.UK). See how to appeal an HMRC penalty.