To register for online filing you'll need your:

• Unique Taxpayer Reference (UTR) – the 10-digit number that appears on any correspondence from HMRC.
• National Insurance number or postcode.

If you don't have a UTR, complete the Registering for Self Assessment form. HMRC will then send you your UTR.

To register for online filing, follow these steps:

1. Go to the registration page on the HMRC website.
2. Click on the relevant option:
   • self-employed or a sole trader
   • not self-employed
   • registering a partner or partnership

After you've registered, HMRC will send you an activation code in the post with a letter telling you how to use it. The code will expire after 28 days. You can file online 48 hours after you activate your account. This delay is due to HMRC systems.