Register for and file your Self Assessment tax return

2. Register if you're self-employed

You’ll need to register for Self Assessment and Class 2 National Insurance as soon as you can after starting your business. You need to do this even if you’ve completed tax returns before.

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

If you’ve sent a return before

Register online (form CWF1).

You’ll need to find your 10-digit Unique Taxpayer Reference (UTR) from when you registered for Self Assessment previously.

If you’ve signed up for the online service before, you should use the same account to file your tax return.

If you haven’t sent a return before

Register online and you’ll:

  • get a letter with your 10-digit Unique Taxpayer Reference (UTR)
  • be enrolled for the Self Assessment online service at the same time

You’ll also get a letter within 10 working days (21 days if you’re abroad) with an activation code. You’ll need this when you first log in to your online account. You can replace an activation code if you don’t 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 can’t save a partly completed form.

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