SA1 Form HMRC: What Is Form SA1 and How to Register for Self Assessment Online?

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If you have been told that you need to register for Self Assessment but you are not self-employed, you may have come across the SA1 form. The SA1 form is used by individuals who need to register for Self Assessment with HM Revenue and Customs (HMRC) for reasons other than being self-employed, and in many cases the registration can now be completed online rather than filling in a paper form and sending it through the post.

What is the SA1 form?

The SA1 form is an HMRC registration form used by individuals who need to register for Self Assessment but are not registering because they are self-employed. For example, you may need to use SA1 if you receive income from a UK rental property, have taxable income from abroad, receive certain untaxed income, need to pay the High Income Child Benefit Charge, or have Capital Gains Tax to report.

This is an important distinction because people who are starting a self-employed business normally register for Self Assessment using a different process, rather than SA1.

HMRC describes SA1 as the form for registering for Self Assessment for reasons other than self-employment.

Who needs to complete an SA1 form?

You may need to complete an SA1 if you are an individual who is not self-employed but have income or another tax liability that means you need to complete a Self Assessment tax return.

Common examples include people who:

• receive rental income from UK property
• receive taxable foreign income
• have untaxed income that cannot be collected through their PAYE tax code
• receive certain income from a trust or settlement
• need to pay the High Income Child Benefit Charge and have not chosen to pay it through PAYE
• have Capital Gains Tax to report.

For example, someone who works for an employer and receives rental income from a property they own may need to register for Self Assessment even though they are not self-employed.

If you are unsure whether you need to register at all, it is better to check your circumstances before completing the form. HMRC has an online service that helps you check when to register for Self Assessment and what registration method you should use.

Is SA1 the same as registering as self-employed?

No. SA1 and self-employed registration are different processes.

If you are starting to work for yourself as a sole trader, you normally register as self-employed with HMRC. If you are not self-employed but need to complete a Self Assessment tax return for another reason, SA1 is generally the relevant registration route.

This distinction matters because choosing the wrong registration route can create unnecessary problems with your HMRC record, particularly if you already have a Self Assessment account or have previously been registered.

Can I complete the SA1 form online?

Yes. You can register for Self Assessment online using HMRC’s online service.

You will need to sign in to your HMRC account, or create the necessary sign-in details if you do not already have them. HMRC says that the online SA1 registration asks for information including your name, address, date of birth, telephone number and National Insurance number if you have one. You will also need to explain why you need to register and give the date when the reason for registration started.

One important point is that you cannot save your progress while completing the online SA1 registration, so it is sensible to have the necessary information available before you start.

Where can I find the SA1 form online?

The easiest option is to use HMRC’s online Self Assessment registration service rather than looking for a downloadable form first.

HMRC’s current guidance provides an online service for people who need to register for Self Assessment for a reason other than self-employment. You can use the service to provide your information and register with HMRC.

HMRC: Register for Self Assessment if you are not self-employed

HMRC also provides a general registration service where you can check which registration route applies to your circumstances.

What information do I need for an SA1 registration?

Before starting the online registration, you should have your personal information ready because the online form cannot be saved part-way through.

You will normally need:

• your full name
• your postal address
• your date of birth
• your daytime telephone number
• your National Insurance number, if you have one
• the reason why you need to register for Self Assessment
• the date when that reason started.

For example, if you are registering because you started receiving rental income, you would need to provide information about the reason for registration and when the relevant circumstances began.

Do I need a National Insurance number for SA1?

HMRC’s guidance states that the SA1 registration requires a valid National Insurance number in the normal case. HMRC’s internal guidance also confirms that the National Insurance number is required to process an SA1 registration, although there are limited exceptions for people who do not have one.

If you have a UK National Insurance number, make sure you enter it correctly when completing the registration.

What happens after I submit the SA1 form online?

After you submit the online registration, HMRC will process your application and set up or reactivate your Self Assessment record where appropriate.

HMRC says that if you registered online, you may be able to obtain your Unique Taxpayer Reference (UTR) sooner through the HMRC app or your Personal Tax Account. If HMRC needs to contact you about the registration, this can take longer during busy periods.

Your UTR is important because you normally need it before you can file a Self Assessment tax return.

How long does an SA1 registration take?

HMRC says it will usually contact you within 21 days of receiving the form, although it can take longer during busy periods. If you register online, you may receive or be able to access your UTR sooner.

It is therefore a good idea not to leave registration until just before your tax return deadline, particularly if this is your first Self Assessment registration and you still need to obtain your UTR.

When should I register for Self Assessment using SA1?

The deadline depends on the tax year and your individual circumstances, but generally you need to tell HMRC by 5 October following the end of the tax year if you need to file a Self Assessment tax return for the previous tax year and you have not previously filed one, or you previously registered but did not need to file a return for the relevant year.

For example, for the 2025/26 tax year, which ended on 5 April 2026, HMRC currently says you must tell it by 5 October 2026 if you need to complete a tax return and meet the relevant conditions.

If you are already receiving income that needs to be reported through Self Assessment, you should not wait until the filing deadline to register.

Can I use SA1 if I receive rental income?

Yes. UK property income is one of the common reasons why an individual who is not self-employed may need to register for Self Assessment using SA1.

For example, suppose you have a normal PAYE job and also own a property that you rent out. You are not necessarily self-employed simply because you receive rental income, but you may still have to register for Self Assessment and report the rental income to HMRC.

Once registered, you will normally report the property income and allowable expenses on the relevant property pages of your Self Assessment tax return.

If you want to understand the return itself, rather than the registration process, you can also read our guide to the SA105 form for UK property income.

Can I use SA1 if I have foreign income?

SA1 can also be used where an individual needs to register for Self Assessment because they have taxable foreign income.

This could include certain types of foreign dividends, interest, pensions or other overseas income, although whether particular income needs to be reported depends on your circumstances and the tax rules that apply to you.

If you are not UK resident, or your circumstances involve complex overseas income, you should check the specific HMRC rules rather than assuming that SA1 is automatically the correct registration route.

Can I use SA1 if I have Capital Gains Tax to pay?

Yes, Capital Gains Tax can be another reason for an individual to register for Self Assessment.

However, Capital Gains Tax has its own reporting rules and deadlines, so you should not assume that completing SA1 is the only action required. Depending on what you sold, when you sold it and the type of gain involved, you may have separate reporting obligations.

Does completing SA1 mean I have filed my tax return?

No. This is one of the most important things to understand about the SA1 form.

SA1 is used to register for Self Assessment. It is not your Self Assessment tax return.

After registering, you will normally receive or be able to obtain your UTR and then complete your Self Assessment tax return for the relevant tax year.

The tax return itself is a separate process. HMRC’s main Self Assessment tax return is the SA100, with additional pages such as SA105 used where they are relevant to your circumstances.

If you want to prepare your own return after registration, our guide on how to do a tax return yourself explains the process in more detail.

Can an accountant complete an SA1 registration for a client?

Yes. Tax agents can register clients for Self Assessment through HMRC’s online agent services, subject to the relevant HMRC requirements and authorisation arrangements.

This can be useful where a client has never been registered for Self Assessment and needs to obtain a UTR before the accountant can prepare and submit their tax return.

The agent registration process is separate from the individual’s personal HMRC account, so it is important to make sure the client information is entered correctly.

What if I was registered for Self Assessment before?

If you have previously been registered for Self Assessment, you should not automatically submit a new SA1 simply because you do not currently have an active return to complete.

HMRC’s current guidance says that if you previously registered but did not send a tax return last year, you may need to reactivate your Self Assessment account rather than registering from scratch. HMRC specifically recommends checking how to register so that your return is processed correctly and delays to refunds or correspondence are avoided.

This is particularly important if you have an old UTR or previously filed Self Assessment returns.

What is the difference between SA1, SA100 and CWF1?

These forms are easy to confuse because they all relate to Self Assessment, but they have different purposes.

SA1 is used to register an individual for Self Assessment for reasons other than self-employment.

CWF1 is used when an individual is registering as self-employed.

SA100 is the main Self Assessment tax return used to report income and calculate the tax due.

In other words, SA1 is about getting registered, while SA100 is about filing the tax return.

Can I file my Self Assessment tax return online after using SA1?

Yes. Once you are registered and have the necessary Self Assessment details, you can generally file your Self Assessment tax return online.

HMRC’s online Self Assessment service allows taxpayers to submit returns, view previous returns, check what they owe and view their tax calculations.

However, you should make sure your Self Assessment record is active before submitting a return, particularly if you have previously registered with HMRC.

What should I do if I am not sure whether I need an SA1?

If you are unsure whether you need to register, the best starting point is HMRC’s online Check how to register for Self Assessment service. It helps determine whether you need Self Assessment and which registration route applies to your circumstances.

The key point is that you should not use SA1 simply because you have some extra income. The correct registration method depends on why you need to complete a Self Assessment tax return.

For example, someone starting a sole trader business will normally have a different registration route from someone who has a PAYE job and receives rental income.

SA1 form online: the key points to remember

The SA1 form is used to register individuals for Self Assessment when they are not registering as self-employed. It is commonly relevant to landlords, people with certain foreign or untaxed income, and individuals with other tax liabilities that need to be dealt with through Self Assessment.

The registration can be completed online through HMRC, and you should have your personal details, National Insurance number and information about why you need to register ready before starting because the online form cannot be saved.

Most importantly, SA1 registration is not the same as filing your Self Assessment tax return. Once registered, you may need to complete and submit a separate tax return, usually using the SA100 together with any supplementary pages that apply to your income.

If you are registering for the first time, it is sensible to start the process early so that you have enough time to receive your UTR, prepare your records and submit your tax return before the relevant deadline.

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