How do I register for self assessment and get a UTR?

Almost every first-time self assessment horror story is the same story: the person tried to register in the second half of January, discovered that two separate letters have to arrive by post before they can file, and missed the deadline. The filing deadline is 31 January; the registration deadline is 5 October, and the gap exists precisely because of the postal steps.

Step by step

1. Work out which registration route applies.There are different forms for becoming self-employed, for a partner in a partnership, and for people who are not self-employed but must file for another reason such as rental income or the High Income Child Benefit Charge. Choosing the right one first time avoids weeks.
2. Register by 5 October following the end of the tax year.For income arising in the year ending 5 April, registration is due by 5 October that autumn. Late registration can attract a failure-to-notify penalty based on the tax due.
3. Have your details ready.National Insurance number, address history, the date the income or trade started, and the nature of the activity. A Government Gateway account, or the details to create one.
4. Wait for the UTR to arrive by post.The Unique Taxpayer Reference is a ten-digit number and it is what identifies you for everything self assessment. It is posted, not shown on screen. Once you have it, it never changes, so record it somewhere durable.
5. Wait for the separate activation code.Enrolling for the online self assessment service triggers a second posted letter with an activation code, which expires. If it lapses you can request another, which takes the same time again.
6. Register for Class 2 National Insurance where relevant.Self-employment registration normally handles this. Class 2 contributions matter because they build State Pension entitlement even when profits are low, and the rules on whether they are due or voluntary have changed — check the current position.
7. Set up your records from day one.A separate account for the income, a place to keep receipts, and a monthly slot to reconcile. GuideHQ has a guide on keeping records for a side income; doing it from the start is far cheaper than reconstructing a year in January.
8. Put the deadlines in a calendar.5 October to register, 31 October for paper returns, 31 January for online filing and payment, and 31 July for the second payment on account if you have one.

Common mistakes

• Leaving registration until January — Two posted letters stand between registering and being able to file. That is weeks, and the deadline does not move for it.
• Losing the UTR — It is recoverable from HMRC correspondence and the app, but the recovery is slow at exactly the time you need it. Record it with your other permanent references.

Questions people ask