Register for and file your Self Assessment tax return

Skip to contents of guide

Register if you're self-employed

If you have to send a tax return and did not send one last year, you need to register for Self Assessment and Class 2 National Insurance.

Register by 5 October in your business’s second tax year. You could be fined if you do not.

If you’ve sent a return online before

Re-register online (form CWF1).

You’ll need your 10-digit Unique Taxpayer Reference (UTR) from when you registered before. You can find your UTR if you do not know it.

If you have not sent a return online before

Register online. When you register, HM Revenue and Customs (HMRC) will:

  • send you a letter with your 10-digit Unique Taxpayer Reference (UTR)
  • set up your account for the Self Assessment online service

If you already have a UTR (for example, if you’ve sent a paper return before or registered by phone), create an account for the online service instead.

What happens next

You’ll get a letter within 10 working days (21 days if you’re abroad) with an activation code for your online account. You’ll need this the first time you sign in. You can get a new activation code if you do not receive it or you lose it.

Other ways to register

You can fill this form on-screen then print off and post to HMRC. You’ll need to have all your information ready as you cannot save a partly completed form.

If you’re using an older browser, for example Internet Explorer 8, you’ll need to update it or use a different browser. Find out more about browsers.