Registering for self assessment – what is form SA1?


Do you have to file your own UK tax return?

Even if you are not self-employed, there are many reasons why you may have to complete your own tax return under the self assessment system.  Many employees have to complete their own tax return, particularly if you have income from other sources in addition to your main job.

And, if you have to register for self assessment as an employed person, you will be asked to complete a SA1 form.  Our guide explains when you have to complete this form and what it involves.

When do you have to register for self assessment if employed?

There are several reasons why you may have to file your own tax return even if you are employed.  The most common reasons are:

  • You are a company director
  • You have income from savings and investments of £10,000 or more
  • You are a minister of religion
  • You have income from property of over £10,000 or more (or over £2,500 after deducting allowable expenses)
  • You have any foreign income liable to UK tax
  • You earn £100,000 or more
  • You are a trustee or personal representative
  • You have Capital Gains Tax to pay

Registering for self assessment

If you do have to complete your tax return, you have to register for self assessment with HMRC.  To do this, you will have to complete a SA1 form.

There are two ways to register for self assessment.  You can either call the HMRC helpline who will run through the contents of the SA1 form with you over the phone.  Alternatively, you can print a SA1 from the HMRC website, complete it and return it by post.

The SA1 form

The SA1 form is relatively straightforward.  You will need to provide information including:

  • Your personal details (name, address, telephone number)
  • Your National Insurance number – you must have a NI number to register for self assessment
  • Any previous Unique Taxpayer Reference (UTR) if you have used the self assessment system before
  • The reason that you are registering for self assessment, including any dates from which these reasons became applicable

Filing your tax return

Once HMRC have received your SA1 form, they will use you with a Unique Taxpayer Reference (UTR).  You will also receive any tax returns that have to be completed immediately.

Once you are registered, you will automatically receive your tax return every April.  If you have chosen to submit your tax return online, you will receive a document called a ‘Notice to File’ instead.


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