How to register for Self Assessment

If you are required to report any type of income on a Self Assessment tax return, you first need to register for Self Assessment with HMRC. This is a straightforward process that you can complete online or by post, depending on your reason for registering. Most people, including sole traders and limited company directors, can register online.

This post explains who needs to register for Self Assessment, the steps required to successfully complete the process, and what tax you will be liable to pay on the income you declare on your Self Assessment tax return.

Do I need to register for Self Assessment?

Self Assessment is an HMRC system that individuals use to declare personal income that is not taxed via PAYE. Through Self Assessment, users can report and pay tax on these earnings.

Many types of people need to register for Self Assessment and complete personal tax returns for HMRC, including:

• self-employed sole traders who earn more than £1,000 in a year
• limited company directors who receive untaxed income
• company shareholders receiving more than £10,000 in dividends in a year
• partners (members) in general partnerships, limited partnerships, and limited liability partnerships (LLPs)
• employees claiming expenses in excess of £2,500 in a tax year
• any individual with an annual taxable income over £150,000
• anyone who receives rental income above £2,500 from UK property or land
• individuals who had to pay Capital Gains Tax when they sold or ‘disposed of’ something that increased in value
• anyone who has to pay the High Income Child Benefit Charge

You may also need to register and send a tax return if you have other types of untaxed income to declare, such as tips and commission, income from savings and investments, or foreign income.

To check whether or not you need to register for Self Assessment, use HMRC’s online Self Assessment tool.

What is the registration deadline?

If you are required to send a return, you must register for Self Assessment before 5 October after the end of the relevant tax year. For example, the registration deadline for the current 2024/25 tax year (6 April 2024 to 5 April 2025) is 5 October 2025.

How to register for Self Assessment as a self-employed person

If you are a sole trader or a partner in a business partnership, you can register for Self Assessment online. As part of the process, you will be required to create a Government Gateway user ID and password. However, if you already have a business tax account, you can sign in with your existing credentials.

When you have completed this step, you will answer a few questions to specify that you want to register for Self Assessment. You’ll then fill in the online registration form with details about you and your business, including:

• your name (and any previous name)
• National Insurance number
• date of birth
• home address
• telephone number and email address
• the reason you need to register
• business name
• business address (if different from your home address)
• the date you started self-employment
• the type of work you do (e.g. plumber)

HMRC’s video on registering for Self Assessment as a self-employed person provides step-by-step guidance on completing each section of the form.

Once you’ve registered, HMRC will enrol you for the Self Assessment Online service. Within approximately 1-2 weeks, you will receive your Unique Taxpayer Reference (UTR) and an activation code in the post. You need these to sign in to your account and activate the Self Assessment service.

You must activate your online account within 28 days. Simply log in with your Government Gateway credentials and enter the activation code when requested. If the code hasn’t arrived after 21 days of registration, you can find out online when to expect your activation code.

You will continue to use your UTR for as long as you report through Self Assessment. You’ll need to provide it whenever you file tax returns, pay self-employed taxes, or contact HMRC about anything else related to Self Assessment.

How to register for Self Assessment as a company director and shareholder

If you are a company director (but not a shareholder), you only need to register for Self Assessment if you receive any untaxed income from the company, or if your salary is over £150,000.

However, if you earn more than this or you receive expenses and taxable benefits, dividends from shares, or any other type of untaxed earnings, you must register and complete an annual tax return.

To begin, create a Government Gateway user ID and password (or sign in to your existing account if you already have one).

Next, visit online.hmrc.gov.uk/shortforms/form/SA1 and sign in to your tax account with your user ID and password. The registration form will appear on-screen. Provide the following information on the form, where applicable:

• your full name, and any previous name
• National Insurance number
• date of birth 
• your personal UTR (if you already have one)
• your residential address and the date you moved there
• telephone number and email address 
• select your reason for registering – e.g. ‘I am a company director’ and/or ‘I’ve untaxed income which cannot be coded in PAYE’
• date on which you received untaxed income

HMRC’s video on registering for Self Assessment if you’re not self-employed (which, as a director or shareholder, you are not) provides step-by-step guidance on successfully completing the registration process.

Within approximately 1-2 weeks, you should receive your UTR (unless you already have one) and an activation code in the post. The UTR relates only to you – it is not the same as your company UTR.

Be sure to activate your online account within 28 days by logging in with your Government Gateway credentials and entering the activation code when requested.

Can I register for Self Assessment by post?

You may need to register for Self Assessment by post rather than online if you:

• receive income from UK land and property
• have taxable foreign income
• have adjusted net income over £60,000 and either you or your partner continue to receive Child Benefit payments
• have yearly income over £150,000
• receive yearly income from a trust or settlement
• receive untaxed income that cannot be collected through your PAYE tax code
• have Capital Gains Tax to pay
• are unable to register online for any particular reason

To register by post, you will need to complete form SA1 online, print it, sign it and enter the date, and then post it to:

HM Revenue and Customs
NIC&EO
BX9 1AN

If this option is not suitable for you and you require a more accessible format, email HMRC [email protected] and specify the format you require.

How do I file a Self Assessment tax return?

You can complete and file your Self Assessment tax return online or by post using form SA100. You can do this yourself or appoint an accountant to take care of it for you. It’s relatively easy to file a return yourself if your accounts are simple and you use HMRC’s free Self Assessment online service.

However, if your accounts are complex and you have to file lots of supplementary pages (e.g. if you’re a director and shareholder, a landlord, or a non-UK resident) you may wish to consult an accountant or other tax specialist for advice.

• Do I need an accountant to do my Self Assessment tax return?
• The top 10 Self Assessment tax return mistakes – and how to avoid them
• 12 Self Assessment expenses you didn’t know you could claim

When filing online, the Self Assessment system will automatically work out your tax and National Insurance liabilities during the process, so you will be told how much you have to pay as soon as you’ve completed the return.

If you need to send your tax return by post rather than online, you must call HMRC to request the paper version of the SA100 tax return. You can download all other supplementary pages you need and include them with the main form.

Self Assessment filing deadline

The deadline for filing your Self Assessment tax return is either midnight on 31 October (for paper returns) or 31 January (for online returns) following the end of the tax year. For example, the filing deadline for the 2024/25 tax year is 31 October 2025 or 31 January 2026.

Provided that you register for Self Assessment and activate your online account by the registration deadline, you can file your tax return at any time after the end of the tax year.

How much tax will I pay through Self Assessment?

Through Self Assessment, you pay the same rates of Income Tax as employed individuals who are taxed through PAYE. Every person born after 5 April 1948 with an annual income below £100,000 is also entitled to the full tax-free Personal Allowance of £12,570.

If you live in England, Wales, or Northern Ireland, any income you receive above the Personal Allowance will be taxed at the following rates of Income Tax:

• 20% basic rate – up to £50,270
• 40% higher rate – between £50,271 and £125,140
• 45% additional rate – income above £125,140

If you live in Scotland, you’ll pay the following rates of Scottish Income Tax on any earnings above the Personal Allowance:

• 19% starter rate – up to £14,876
• 20% basic rate – between £14,877 and £26,561
• 21% intermediate rate – between £26,562 and £43,662
• 42% higher rate – between £43,663 and £75,000
• 45% advanced rate – between £75,001 and £125,140
• 48% top rate – income above £125,140

You can use HMRC’s online self-employed tax calculator to estimate your tax bill for the current 2024/25 tax year.

What about tax on dividends?

If you are a company shareholder and need to pay tax on dividend income, you will pay the following rates of dividend tax:

• 8.75% – dividend income that falls within the basic-rate Income Tax band
• 33.75% – dividend income that falls within the higher-rate Income Tax band
• 39.35% – dividend income that falls within the additional-rate Income Tax band

To work out your dividend tax, you need to add together your income from all sources (e.g. salary and dividends) to determine which tax band(s) apply to you.

What National Insurance will I pay through Self Assessment?

Most people who are registered for Self Assessment are required to pay Class 4 National Insurance contributions (NICs). From 6 April 2024, the requirement to pay Class 2 on earnings above £12,570 no longer applies to self-employed people.

If your annual profits are £6,725 or more, Class 2 NICs are treated as having been paid, so your National Insurance record is protected. However, if you earn less than this, you can choose to pay voluntary contributions.

The National Insurance you will pay on income earned in 2024/25 will be calculated when you complete your Self Assessment tax return after the end of the tax year.

• Class 4 is charged at 6% on profits between the Lower Profits Limit (£12,570) and the Upper Profits Limit (£50,270), then 2% on profits above £50,270
• Voluntary Class 2 contributions are £3.45 per week

National insurance should be paid through Self Assessment by midnight on 31 January after the end of the tax year. This means that your NICs for the 2024/25 tax year are due by 31 January 2026.

Thanks for reading

We hope this post has provided you with the required knowledge to feel confident registering for Self Assessment with HMRC. It’s pretty straightforward and easy to do, so you shouldn’t have any difficulty.

However, we do recommend appointing an accountant to help you with your tax returns. They will also be able to advise on ways to minimise your tax burden.

Check out the 1st Formations Blog for more business advice, insights, and guidance.