Register for and file your Self-Assessment tax return

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 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.

If YOU HAVE 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.

To Pay your Self-Assessment to HMRC


Where to find your UTR

Your UTR is on previous tax returns and other documents from HMRC, for example:

  • notices to file a return
  • payment reminders

You can also find your UTR in your HMRC online account.

If you cannot find your UTR

Call the Self-Assessment helpline to request your UTR if you cannot find any documents from HMRC.