How to Register for Self Assessment and Get Your UTR Number (Part 2)

Quick answer

Registering for self assessment is a two-stage process: first you tell HMRC you need to file (which generates your UTR number), and then you set up access to HMRC's online services to submit the return itself. Both stages involve post — HMRC sends your UTR and a separate Government Gateway activation code by letter. The whole process from registration to having a functioning online account typically takes three to four weeks, which is why the registration deadline is set well before the January filing date.

This is Part 2 of the UK Self Assessment From Scratch series. Part 1 covered whether you need to file at all. This part walks you through every step of registration, explains what a UTR is and where to find it, and covers what to do if things go wrong.

What is a UTR number?

A Unique Taxpayer Reference (UTR) is the 10-digit reference HMRC uses to identify your individual tax record. It takes the format 12345 67890 (sometimes displayed as 10 consecutive digits, sometimes with a space in the middle).

Key facts about your UTR:

• It is assigned for life — you keep the same UTR even if you stop filing for years and restart later.
• It identifies you to HMRC across all tax matters — income tax, self assessment, Corporation Tax (if you later set up a company), and more.
• It appears on SA302 documents (your tax calculation), P800 notices, all HMRC letters related to self assessment, and at the top of your tax return.
• It is different from your National Insurance number — your NI number takes the format AB 12 34 56 C and relates to your NI contributions record. You need both to file.
• If you set up a limited company in future, the company gets its own separate 10-digit Corporation Tax UTR — distinct from your personal one.

Treat your UTR as confidential. It is used alongside your NI number and date of birth to verify your identity with HMRC — sharing it carelessly can expose you to identity fraud.

The three registration routes

Route 1: Online registration at gov.uk (recommended)

The fastest and most straightforward method for most people. Go to gov.uk/register-for-self-assessment and select the option that matches your situation:

• Self-employed — for sole traders, freelancers, contractors, and gig workers
• Not self-employed — for rental income, savings and investment income, or other untaxed income
• Partnership — if you are a partner in a business partnership

The online form takes 15–20 minutes to complete. You will need:

• Your National Insurance number
• Your date of birth and address
• The date your self-employment or other income started
• Your business name and activity (if self-employed)

Route 2: CWF1 form (self-employment, paper)

The CWF1 is the paper registration form for self-employment. It registers you for both self assessment and Class 2/4 National Insurance at the same time. Download it from gov.uk or call HMRC to request a paper copy. Use this route only if you cannot complete the online registration — postal registration takes significantly longer.

Route 3: SA1 form (other income, paper)

The SA1 is for people who need to file a return but are not self-employed — for example, someone with rental income, overseas income, or high employment earnings above £100,000. Like CWF1, it is a paper form available from gov.uk. If you are submitting close to the 5 October deadline, use the online route instead.

Step-by-step: online registration

Here is the complete process from start to finish.

Step 1: Go to gov.uk/register-for-self-assessment

Navigate to the page and click "Register if you're self-employed or a sole trader" or "Register if you're not self-employed", depending on your situation. You will be taken through HMRC's registration flow.

Step 2: Sign in or create a Government Gateway account

You need a Government Gateway account to register online. If you have used Government Gateway before (for example, for PAYE, Child Benefit, or a previous self assessment year), sign in with your existing credentials.

If you are new to Government Gateway, click "Create sign-in details". You will need to:

1. Provide your email address and create a password.
2. Verify your email address via a confirmation link.
3. Note your Government Gateway user ID — HMRC emails this to you (it looks like a 12-digit number: 123 456 789 012). Store it somewhere safe — you will need it every January.

Step 3: Verify your identity

HMRC requires identity verification before activating your account. You will be asked to confirm your identity using two of the following:

• Your National Insurance number
• A valid UK passport
• A UK driving licence
• A credit file check (via a third-party provider)
• P60 from a previous employer
• A recent payslip

The system runs a credit-bureau style check in the background — this is a "soft" check and does not affect your credit rating.

Step 4: Complete the self assessment registration form

Once your identity is verified, you complete the actual registration. Key questions include:

• Why are you registering? (Self-employment, rental income, high income, Child Benefit charge, etc.)
• Date you started your business or when you first received the relevant income
• Business name (if self-employed — can be your own name)
• Type of business activity (a broad category such as "IT consulting", "private tutoring", "property letting")
• National Insurance number

For self-employed registrations, you will also be asked about your accounting period — most sole traders use 5 April as their accounting year-end to match the tax year, which simplifies the return.

Step 5: Submit and wait for your UTR

After submitting the online form, HMRC creates your self assessment record. You will receive two letters at your registered address:

Letter 1 — Your UTR: arrives within 10 working days. Headed "Your Unique Taxpayer Reference" and shows your 10-digit UTR. Keep this letter permanently.

Letter 2 — Government Gateway activation code: arrives separately, also within 7–10 working days of account creation. This is a short code (typically 12 characters) you need to activate your online self assessment access. It has an expiry date — usually 28 days from issue.

Step 6: Activate your online account

Log back into Government Gateway, navigate to your self assessment service, and enter the activation code when prompted. Once entered, your self assessment account is live and you can file returns, view your tax position, and set up payment arrangements.

If your activation code expires before you use it, request a new one through Government Gateway — the replacement also comes by post.

Registration deadlines and what happens if you miss them

The registration deadline for self assessment is 5 October following the end of the relevant tax year.

Missing the registration deadline can result in a penalty of up to £100. More practically, a late registration means your UTR may not arrive until October or November, which compresses the time you have to prepare and file before the 31 January deadline.

If you have already missed the 5 October deadline: register as soon as possible. HMRC does not automatically impose a penalty in every case — a genuine first-time registrant who was unaware of the requirement and registers promptly will often have the penalty reduced or waived. But you must act immediately, not wait until the New Year.

If you owe tax but register late: once you file, interest runs from 31 January on any outstanding balance, regardless of when you registered. You cannot avoid the interest clock by delaying registration.

After registration: setting up HMRC Online Services properly

Once your Government Gateway account is active, take 20 minutes to set it up fully before you need to file.

Your Personal Tax Account

Go to gov.uk/personal-tax-account. This is HMRC's dashboard showing your income tax position, NI record, self assessment status, and correspondence. Key things to check:

• Confirm your address and contact details are correct (HMRC uses these for all post)
• View your NI record — particularly important if there are gaps you might want to fill with voluntary contributions
• Download any SA302 documents from previous years if you need proof of income for a mortgage or rental application

The HMRC app

Download the HMRC app from the App Store or Google Play. Once logged in with your Government Gateway credentials, the app shows:

• Your UTR (useful if you lose the original letter)
• Your current tax code and income estimates
• Any messages from HMRC
• Your self assessment return status

The app is particularly useful for checking your UTR at short notice — for example, if a bank asks for it.

Two-factor authentication

Enable two-factor authentication (2FA) on your Government Gateway account if you have not already. HMRC sends a code to your mobile each time you log in. This protects against fraudulent access — tax account fraud is increasingly common, and attackers use compromised credentials to alter bank account details for repayments.

Sign up for paperless communications

HMRC can send notices, statements, and reminders by email rather than post. Opt in via Government Gateway — this means you receive important notices (such as your 31 January reminder or a tax calculation) much faster, and you will not miss them because post was lost or went to a previous address.

Business registration for self-employed people

When you register for self assessment as self-employed, HMRC automatically registers you for Class 4 National Insurance, which is paid through your self assessment return each January.

However, there are two additional registrations you may need to handle separately:

Class 2 National Insurance (voluntary)

Class 2 NI was abolished as a compulsory payment from April 2024. However, if your self-employment profits are below the Small Profits Threshold (£6,845 for 2025/26), you can choose to pay Class 2 voluntarily (£3.45 per week for 2025/26) to protect your entitlement to the State Pension and certain benefits. You opt in via your self assessment return each year.

VAT registration

If your taxable turnover exceeds £90,000 in any rolling 12-month period, you must register for VAT. This is completely separate from self assessment registration — you register at gov.uk/vat-registration and receive a VAT number separately. Once registered, you collect VAT from customers, file quarterly VAT returns, and pay the net VAT balance to HMRC.

If you are close to the threshold, monitor your rolling 12-month turnover carefully. You must register within 30 days of exceeding it, and late VAT registration carries its own penalty regime. Under Making Tax Digital, VAT-registered businesses must already use MTD-compatible software for VAT.

How to find your UTR if you have forgotten it

Lost your UTR letter? Here are four ways to find it:

If you use accounting software (FreeAgent, QuickBooks, Xero), it will typically have your UTR stored once you have connected it to HMRC's systems.

Overseas residents registering for UK self assessment

If you are not resident in the UK but have UK income (UK rental property, UK employment, UK dividends), you still have a self assessment obligation. The process is slightly different:

• Register using the SA1 form by post — the online registration does not work for non-UK addresses in all cases.
• You will also need to complete SA109 (statutory residence and remittance basis) to declare your residence status.
• Your UTR will be posted to your overseas address — allow up to 21 days for international post.
• If you use a UK-based tax agent, they can register on your behalf via HMRC's Agent Services Account.

What comes next

Once you have your UTR and your Government Gateway account is active, the next step is preparing to complete your return — which means gathering all your income records and understanding which supplementary pages you need. Part 3 of this series covers exactly that: How to Declare All Your Income on Self Assessment: Employment, Rental, Dividends and More.