If you have started working for yourself, received rental income for the first time, or found yourself in a situation where not all your tax is collected through PAYE, registering for Self Assessment is the first step. It sounds complicated, but the process itself is straightforward once you know what is needed.
This guide explains who needs to register, how to do it, and what happens after you have submitted your registration.
Quick Answer
You register for Self Assessment by creating a Government Gateway account and completing the online registration form at gov.uk. Once registered, HMRC sends you a Unique Taxpayer Reference (UTR) by post within 10 working days. You must register by 5 October following the end of the first tax year in which you needed to file.
Who Needs to Register?
You need to register for Self Assessment if you:
- Are self-employed as a sole trader and earned more than £1,000 in the tax year
- Received rental income from a property
- Earned more than £100,000 in total income
- Received untaxed income from savings, dividends or investments above certain thresholds
- Need to pay Capital Gains Tax on a disposal
- Are a company director with income not taxed through PAYE
- Received Child Benefit and either you or your partner earned over £60,000
If you are already registered and have filed before, you do not need to register again.
When Do You Need to Register?
The registration deadline is 5 October following the end of the relevant tax year. So if you became self-employed or received rental income for the first time during the 2024/25 tax year (which ended 5 April 2025), you must register by 5 October 2025.
Registering late does not mean you cannot file, but HMRC may issue a penalty for the late registration in some circumstances. Acting before the deadline avoids this.
How to Register: Step by Step
Step 1: Create a Government Gateway Account
If you do not already have one, go to gov.uk and create a Government Gateway account. You will need:
- Your National Insurance number
- A form of photo ID (passport or driving licence)
- Your email address
If you already have a Government Gateway account from a previous employer or for another HMRC service, use the same login.
Step 2: Choose the Right Registration Route
The registration form you complete depends on your circumstances:
- Self-employed sole trader: Use the SA1 form or the online registration for self-employment at gov.uk
- Landlord or other untaxed income: Use the SA1 form
- Partner in a business partnership: Use the SA401 form
Most people use the online registration service, which guides you through the questions and is quicker than a paper form.
Step 3: Provide Your Details
You will need to provide:
- Your full name, date of birth, and National Insurance number
- Your address
- The nature of your income (self-employment, property, etc.)
- The date you started the relevant activity
For self-employment, you will also need to give your business name (which can simply be your own name), your business address, and a brief description of what you do.
Step 4: Wait for Your UTR
Once you have submitted the registration, HMRC will send your Unique Taxpayer Reference (UTR) by post to your registered address within 10 working days. Keep this safe. You will need it every time you file a return or communicate with HMRC about your Self Assessment.
Your UTR is a 10-digit number that stays with you permanently.
Step 5: Activate Your Self Assessment Online Account
After receiving your UTR, you need to activate the Self Assessment section of your Government Gateway account. HMRC sends a separate activation code by post, which you enter to complete the setup. Allow up to 10 working days for this.
Once activated, you can file your returns, check your tax account, and manage payments online.
What Happens After Registration?
Once registered, HMRC will issue you with a notice to file for each tax year. You will need to complete and submit your Self Assessment return by 31 January following the end of the relevant tax year and pay any tax owed by the same date.
HMRC will also set up your payment on account obligations if your tax bill exceeds a certain threshold, which involves making advance payments towards the following year’s liability in January and July.
What If You Register Late?
If you miss the 5 October registration deadline, register as soon as possible anyway. The penalty for late registration is based on a percentage of the unpaid tax, and HMRC has some discretion where there is a reasonable excuse. Acting promptly is always better than waiting.
If you were supposed to register years ago and have not, a tax specialist can help you work through the outstanding years, file the returns, and engage with HMRC to resolve any penalties on a manageable basis.
FAQs
I was self-employed briefly for just a few weeks. Do I still need to register? Yes, if your gross income from self-employment exceeded £1,000 in the tax year. The threshold is based on total income before expenses, not profit.
I registered last year. Do I need to re-register this year? No. Once registered, your Self Assessment account remains active. You simply file your return each year. However, if you believe you no longer need to file (because your circumstances have changed), you must contact HMRC to deregister, otherwise they will continue to expect a return.
I have not received my UTR yet. Can I still file? You cannot file without a UTR. If it has been more than 15 working days since you registered and you have not received it, contact HMRC. If the deadline is approaching, a tax specialist can chase this on your behalf.
Can someone else register on my behalf? Yes. A tax agent can register you for Self Assessment using a form 64-8 to establish their authority to act. This is the most common approach when using a tax specialist from the start.
I am a landlord who has had rental income for several years but never registered. What should I do? Register now and contact a tax specialist. You will likely need to file returns for previous years. Acting voluntarily before HMRC contacts you results in significantly lower penalties than being discovered.
Register Now and Get Set Up Correctly
Our principal tax adviser is an ACCA and ATT qualified tax specialist and HMRC Registered Agent with over 25 years of personal tax experience. Kent Tax Specialists can register you for Self Assessment, handle all HMRC correspondence, and prepare your returns accurately from the start. We serve clients across Gravesend, Dartford, Maidstone, Medway, Sevenoaks, Tonbridge, Tunbridge Wells, Canterbury and the wider Kent area. Get in touch today.
Also see: Self Assessment in Gravesend | Self Assessment in Dartford | Self Assessment in Tonbridge
