How to register for a self assessment tax return?

PHS Team

14 Sep, 2026

You can register online through HMRC’s Self Assessment registration service using the route that matches your circumstances.

Starting Self Assessment for the first time can feel confusing, especially when you are unsure whether you need to register or when to do it. If you have recently become self-employed, joined a business partnership, or started earning income that is not fully taxed through PAYE, you may need to register with HM Revenue and Customs (HMRC). 

Getting registered on time can help you avoid unnecessary stress, keep your tax records organised and prepare for your tax bill. The process is not the same for everyone, so understanding which registration route applies to you is an important first step. 

How to Register for Self Assessment 

The registration process depends on why you need to file a Self Assessment tax return. Before starting, you should check whether you actually need to register.

For example, HMRC says you may need to submit a return if you:

• Were self-employed as a sole trader and earned more than £1,000 before allowable expenses.
• Were a partner in a business partnership.
• Had taxable income from property or land.
• Received certain foreign income.
• Had other untaxed income, such as dividends or savings interest.
• Need to pay the High Income Child Benefit Charge and have not chosen to pay it through PAYE.
• Had a Capital Gains Tax liability.

The £1,000 trading-income threshold applies to sole traders, although there can be other circumstances in which you may choose or need to complete a tax return.

Once you have established that you need to file, the next step is to choose the registration route that matches your circumstances.

When to Register for Self Assessment

Knowing when to register for Self Assessment is just as important as knowing how to do it.

If you became self-employed during the 2025/26 tax year, which runs from 6 April 2025 to 5 April 2026, you generally need to notify HMRC by 5 October 2026 if you are required to complete a Self Assessment return.

You should not wait until January to think about registration. Registration comes before filing your first tax return, and you need time to receive the information and tax references required to manage your Self Assessment obligations.

Example

Suppose Sarah started working as a freelance graphic designer in July 2025 and her trading income exceeded the relevant threshold.

Her tax year would run from July 2025 to 5 April 2026. She should register by 5 October 2026 and then submit her online Self Assessment return and pay any tax due by 31 January 2027.

Registering early gives Sarah more time to organise invoices, receipts, business expenses and bank records before completing her return.

The Self Assessment Registration Deadlines

Understanding the key dates can make tax planning much easier.

For the 2025/26 tax year, the main dates include:

If you register after 5 October 2026, HMRC may give you a different filing deadline, but you will still generally need to pay tax owed by the applicable payment deadline.

Late registration can potentially result in penalties, so it is sensible to check your obligations as soon as you start receiving taxable income.

Registering if You’re Self-Employed

If you operate as a sole trader, you generally register for Self Assessment using HMRC's online service. HMRC's current registration service helps you determine the appropriate registration route based on your circumstances.

You should have relevant personal and business information available before starting.

This may include:

• National Insurance number
• Personal details
• Business or trading information
• The date you started self-employment
• Details of your business activities
• Contact information
• Information about your income and records

After registering, HMRC will provide the relevant tax information, including your Unique Taxpayer Reference (UTR), which you will need when dealing with your Self Assessment obligations.

If You Don't Already Have a Business Tax Account with HMRC

If you are new to self-employment, you may not already have an online business tax account. This does not prevent you from registering.

HMRC’s online service guides you through the relevant registration steps.

Recent improvements to the registration process have made it easier for new taxpayers to register through their Personal Tax Account.

Once registration is complete, keep your UTR (Unique Taxpayer Reference) and other HMRC correspondence safely.

You will need your UTR and HMRC information when filing your tax return or communicating with HMRC.

Start keeping financial records from the beginning, including:

• Sales records
• Invoices
• Allowable expenses
• Receipts
• Business-related bank transactions

Good record keeping can make preparing and filing your Self Assessment tax return significantly easier.

Registering if You're a Partner in a Partnership

Joining a business partnership creates different responsibilities from operating as a sole trader.

The nominated partner is responsible for registering the partnership for Self Assessment and completing the partnership tax return. The partnership can register using HMRC's partnership registration process, while individual partners generally need to register separately and submit their own Self Assessment tax returns.

HMRC states that the partnership generally needs to be registered by 5 October in the business's second tax year.

For example, if you become a partner during the 2025/26 tax year, you should consider the relevant registration requirements and deadlines early rather than waiting until the partnership's accounts are prepared.

Keeping clear records of each partner's share of profits is particularly important because the information from the partnership return will feed into the partners' individual tax returns.

Registering if You're Not Self-Employed or in a Partnership

Not everyone who needs to file a Self Assessment is self-employed.

If you are not self-employed and need to register for another reason, HMRC generally uses form SA1 for registration. This may apply to people with certain types of untaxed income, such as property income, taxable foreign income or other circumstances requiring Self Assessment.

Your circumstances determine whether you need to register and which information you must provide.

For example, an individual receiving taxable rental income may have Self Assessment obligations even though they do not operate as a sole trader. Similarly, someone with certain foreign income may need to report it through Self Assessment.

A Simple Registration Checklist

Before registering, consider the following:

1. Check whether you need to file a return.
2. Identify why you need Self Assessment.
3. Choose the correct HMRC registration route.
4. Gather your personal and income information.
5. Register before the applicable deadline.
6. Keep your UTR and HMRC correspondence safe.
7. Maintain accurate financial records.
8. Plan ahead for your tax payment.

Taking these steps early can reduce the risk of missing important deadlines.

Conclusion

Registering for a Self Assessment tax return correctly and meeting HMRC deadlines can help you avoid unnecessary complications. However, understanding your obligations and keeping accurate records can be challenging.

PHS Associates offers professional accounting and tax support to individuals, self-employed professionals and businesses across the UK. We can help with registration, record keeping, tax returns and HMRC deadlines.

Need help with your Self Assessment? Book free consultation today for expert and reliable tax support.

Frequently Asked Questions