The Number Everyone Asks For
Sooner or later someone asks for your UTR. Your accountant needs it to file your tax return. A construction contractor won't pay you properly without it. A mortgage broker wants it to check your income. And if you have just started working for yourself, you may not have one yet.
A UTR, or Unique Taxpayer Reference, is a 10-digit number HMRC uses to identify you, or your company, in its systems. It is issued when you register for Self Assessment or when a limited company is set up. HMRC sometimes just calls it your "tax reference".
This guide covers who gets one, how long it takes, where to find a lost one and how it differs from the other numbers HMRC gives you. It is timely. The deadline to register for Self Assessment for the 2025/26 tax year is 5 October 2026, and registering is how most people get a UTR in the first place.
What a UTR Number Looks Like
A UTR is ten digits, for example 12345 67890. HMRC letters often print it with a space in the middle, and some show it with a K on the end. The K is not part of the UTR itself. It turns the UTR into your Self Assessment payment reference, which we cover below.
There are no letters in a UTR, and it does not encode anything about you. It is simply a reference number, and it stays with you for life. If you stop being self-employed and start again ten years later, HMRC will normally reactivate your old UTR rather than issue a new one.
Personal UTR vs Company UTR
There are two kinds, and mixing them up is one of the most common problems we see.
- A personal UTR belongs to you as an individual. You get it when you register for Self Assessment, for example as a sole trader, a landlord, or someone with untaxed income above the trading allowance.
- A company UTR belongs to a limited company. It is used for Corporation Tax, and HMRC issues it after the company is incorporated at Companies House.
If you are a director of your own company, you may have both. They are completely separate numbers. Filing a company's Corporation Tax return under the director's personal UTR, or quoting the company's UTR on a personal tax return, causes problems that can take months to unpick.
Partnerships add a third layer. The partnership has its own UTR for the partnership return, and each partner also has their own personal UTR for their individual return. Trusts and estates get their own UTRs too.
Who Needs a UTR?
You need a personal UTR if you have to file a Self Assessment tax return. The most common reasons are:
- You are self-employed and your trading income is over £1,000.
- You receive rental income from property, which we explain in our guide to tax on rental income.
- You have a capital gain to report, such as on a second property or shares. See our guide to capital gains tax.
- You have untaxed income such as foreign income, large amounts of savings interest, or dividends above the allowance.
- You are a partner in a business partnership.
You do not need a UTR just because you have a job. If all your income comes through PAYE, your employer deducts the tax and HMRC already knows about you through your National Insurance number.
Being a company director is no longer, on its own, a reason to register. HMRC changed its criteria from the 2023/24 tax year onwards, so a director whose only income is a salary taxed through payroll may not need a return at all. Most owner-managed company directors still file one, because they take dividends above the dividend allowance. If you are unsure, our sole trader vs limited company guide explains how the two structures are taxed.
How to Get a UTR Number
You don't apply for a UTR directly. It is a by-product of registering.
For individuals, you register for Self Assessment on GOV.UK. If you are starting a business, you register as self-employed. If you need a return for another reason, such as rental income, there is a separate route for people who are not self-employed. HMRC then sends your UTR by post.
For limited companies, HMRC finds out about the company from Companies House and posts the UTR to the company's registered office address. If it doesn't arrive, you can request it online through GOV.UK and HMRC will post it again to the same address.
Registering is free. You never need to pay anyone to "apply for a UTR" for you. There are websites that charge for this, and all they do is fill in the same free GOV.UK form.
How Long Does a UTR Take to Arrive?
GOV.UK says you will usually get your UTR by post around 15 days after you register, and that it takes longer if you live overseas.
That 15 days is a typical figure, not a promise. In our experience it stretches during busy periods, and the busiest period of all is the weeks either side of the 5 October deadline. It is also only half the job. To file online you also need to set up your HMRC online account, which involves an activation code that also comes by post.
In practice, plan for three to four weeks between registering and being able to file. That is fine if you register in the summer. It is a problem if you register in January.
The 5 October Deadline, With a Worked Example
The registration deadline is 5 October after the end of the tax year in which you had the income. It catches people out because it comes almost four months before the filing deadline, so it feels like an earlier, less important step. It isn't.
Take Priya, who left her job in November 2025 to work as a freelance designer. Her income came in from December onwards. Here is her timeline for the 2025/26 tax year, which ran from 6 April 2025 to 5 April 2026 (our UK tax year guide explains the dates).
| Date | What happens |
|---|---|
| 5 April 2026 | Her first tax year as a freelancer ends |
| 5 October 2026 | Deadline to register for Self Assessment and get a UTR |
| Around 20 October 2026 | UTR arrives if she registers on the deadline |
| 31 January 2027 | Deadline to file her online return |
| 31 January 2027 | Deadline to pay her 2025/26 tax, plus her first payment on account for 2026/27 if her bill is over £1,000 |
If Priya registers on 15 December instead, she will probably still get her UTR in time to file. She has still missed the registration deadline, and HMRC can charge a penalty for failure to notify.
Here is the part most guides leave out. The failure to notify penalty is a percentage of the tax that is still unpaid on 31 January. If Priya registers late but files her return and pays everything she owes by 31 January 2027, there is no unpaid tax for the penalty to bite on, so in practice there is usually nothing to charge. Where tax is unpaid, the penalty for a careless (non-deliberate) failure is up to 30 percent, and it can be reduced to nil if you tell HMRC yourself, before they find you, within 12 months.
So missing 5 October is not a disaster. What turns it into one is missing 5 October, then also missing 31 January because the UTR and activation code arrived too late.
How to Find Your UTR Number
If you have had a UTR before, it is written down in more places than you might think.
- Your HMRC personal tax account. Sign in on GOV.UK and it is shown in the Self Assessment section.
- The HMRC app. It shows your UTR once you have signed in, which is the quickest option for most people.
- Previous tax returns. Any copy of a past SA100 has it on the front page.
- HMRC letters. Your notice to file a return, statements of account and payment reminders all show it, usually near the top right.
- Your accountant. If someone has filed for you before, they will have it on file.
For a company UTR, look at previous Corporation Tax returns, HMRC letters addressed to the company, and the company's HMRC online account. Your accountant will also hold it.
If none of those work, you can ask HMRC for it. They will post it to the address they hold for you, so if you have moved since you last dealt with them, update your address first or it will go to your old home.
The Company UTR Letter Nobody Opens
One problem comes up again and again when we take on new limited company clients. The company UTR letter goes to the registered office. Many people set up their company through a formation agent and use the agent's address as the registered office, often as part of a cheap package. The letter arrives at an office the director has never visited, and it gets forwarded months later, if at all.
The director doesn't notice until the first Corporation Tax return is due, usually around 12 months after the company's year end. Then there is a scramble to find a number that was posted to someone else.
If you used a formation agent, ask them about mail forwarding the week you incorporate. If you haven't had a UTR within a month, request it again straight away rather than waiting.
Paying HMRC: The UTR and the Letter K
Your UTR is also the basis of your payment reference, and getting this wrong means your money sits unallocated while HMRC sends you reminders.
- Self Assessment: the payment reference is your 10-digit UTR followed by the letter K, making 11 characters in total. If your UTR is 1234567890, you pay with the reference 1234567890K.
- Corporation Tax: the payment reference is a 17-character reference that starts with the company UTR but includes extra characters for the accounting period. It is shown on the notice to deliver a return, on reminders and in the company's HMRC online account. Do not just use the 10-digit UTR, and do not reuse last year's reference for this year's bill.
We see payments go astray every year because someone paid Corporation Tax using the director's personal UTR plus K. HMRC treats that as a personal Self Assessment payment, which can leave the company showing as late and the director showing as in credit.
UTR vs Other HMRC and Companies House Numbers
| Number | Who has it | What it looks like | What it is for |
|---|---|---|---|
| Personal UTR | Individuals who file Self Assessment | 10 digits | Self Assessment returns and payments |
| Company UTR | Limited companies | 10 digits | Corporation Tax |
| National Insurance number | Almost everyone who works in the UK | Two letters, six digits, one letter, e.g. QQ123456C | NI contributions, PAYE, state benefits |
| Company registration number | Limited companies | Usually 8 characters, e.g. 01234567 | Companies House filings |
| VAT registration number | VAT-registered businesses | 9 digits, often with a GB prefix | VAT returns and invoices |
| Employer PAYE reference | Businesses that run payroll | Three digits, a slash, then letters and numbers, e.g. 123/AB45678 | Payroll reporting |
Your UTR and your National Insurance number do different jobs and you can't swap one for the other. Your tax code and your P60 relate to PAYE and show your NI number, not your UTR.
UTRs and the Construction Industry Scheme
If you are a subcontractor in construction, a UTR has a direct effect on your cash flow. To register for the Construction Industry Scheme you need a UTR. Registered subcontractors have 20 percent deducted from their labour payments. Unregistered subcontractors have 30 percent deducted.
On a £4,000 labour invoice that is £400 more held back each time, until you claim it back through your tax return months later. Contractors also need your UTR to verify you with HMRC before they pay you. Getting registered before you start your first job is one of the cheapest cash flow wins available to a new subcontractor.
UTRs and Making Tax Digital
From 6 April 2026, sole traders and landlords with qualifying income over £50,000 have to keep digital records and send quarterly updates under Making Tax Digital for Income Tax. The threshold falls to £30,000 from April 2027 and £20,000 from April 2028.
You sign up for Making Tax Digital using your existing Self Assessment details, so you need a UTR first. If you are newly self-employed and expect to cross one of those thresholds, register for Self Assessment early. Doing all of it at once in the weeks before your first quarterly deadline is avoidable stress.
Keeping Your UTR Safe
A UTR on its own is not a password. Knowing it doesn't let someone into your tax account. But combined with your name, address, date of birth and National Insurance number, it is a useful piece of the puzzle for anyone trying to impersonate you to HMRC or a lender.
Share it with your accountant, CIS contractors and lenders who genuinely need it. There is no reason to put it on invoices or in email signatures.
Be wary of messages that mention your UTR or a "tax refund". HMRC does not tell you about refunds by text or email, and it does not ask for bank details that way. The fake messages often look convincing, especially around the January deadline when people expect to hear from HMRC.
What We Think
The UTR is the weakest link in Self Assessment. Almost every other step can be done online in minutes. The one piece that still relies on the post, plus a second posted activation code, is the piece that determines whether you can file at all. Until HMRC issues UTRs on screen at the point of registration, the practical deadline is weeks earlier than the official one.
Treat 5 October as 5 September. If you have started a side business, let a property or sold an asset this year, register as soon as you know. There is no downside to registering early. If it turns out you don't need to file, you can tell HMRC and they will close the record.
Keep your tax numbers together. Most of the "lost UTR" calls we get are from people who had it all along in an old HMRC letter. Put your UTR, National Insurance number and Government Gateway user ID in a password manager or a single secure note the day they arrive. It saves an hour of searching every January.
Don't pay for something that is free. Paid "UTR application" services add a fee and a middleman to a free form. If you want help, pay for someone who will also file the return and give you advice, not someone who will just type your details into GOV.UK.
How IAK Can Help
We register new clients with HMRC, chase UTRs that haven't arrived and make sure the right number goes on the right return.
Our personal tax team handles Self Assessment registration, online account setup and filing for sole traders, landlords, contractors and directors. Our accounting team looks after limited companies from incorporation, including chasing the company UTR and setting up the correct Corporation Tax payment references. For creators and freelancers with income from several platforms, our guide to accounting for influencers covers what to register for and when.
If you have started earning outside a job this year and haven't registered yet, there is still time before 5 October. Get in touch for a free consultation.
Sources
- Find a lost UTR number, GOV.UK, on what a UTR is, where to find it and the typical 15-day wait for a new one.
- Register for Self Assessment, GOV.UK, on the 5 October 2026 registration deadline for the 2025/26 tax year.
- Pay your Self Assessment tax bill: bank details, GOV.UK, on the 11-character payment reference made up of your UTR followed by K.
- Pay your Corporation Tax bill: reference number, GOV.UK, on the 17-character Corporation Tax payment reference.
- Finance Act 2008, Schedule 41, legislation.gov.uk, the legislation for failure to notify penalties and how they are calculated.
- What you must do as a Construction Industry Scheme subcontractor, GOV.UK, on registering for CIS and the 20 percent and 30 percent deduction rates.
- Use Making Tax Digital for Income Tax, GOV.UK, on who must sign up and the income thresholds from April 2026.