What information do you need when you register for Self Assessment?

More than 660,000 people in the UK start their own business each year. Most choose to become self-employed (AKA a sole trader). Sole traders make up about 60% (3.5m) of the total UK business population of…

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Last Updated: 5th April 2023

More than 660,000 people in the UK start their own business each year. Most choose to become self-employed (AKA a sole trader). Sole traders make up about 60% (3.5m) of the total UK business population of 6m, and this includes legions of freelancers, contractors and agency workers.

When you become a sole trader, you must let HMRC know, so that you can declare your earnings and pay Income Tax and your National Insurance contributions (NICs). You do this by filling out a Self Assessment tax return each year, detailing your earnings and costs, so that HMRC can work out how much tax you owe.

Who else must register for Self Assessment?

If you go into business with others in an “ordinary partnership”, all partners must each register for Self Assessment (if earnings are more than £1,000). If you’re employed by someone else but occasionally take on other work from which you earn more than £1,000 within a tax year, you must also register for Self Assessment.

The same is true if you receive tips totalling more than £1,000 a year, because these are classed as additional earnings and they’re subject to Income Tax. Income Tax is also payable on money you earn from renting out a property, so, you’ll also need to register for Self Assessment. This also goes for income from overseas or savings, investments and dividend payments if you own shares.

Need to know! To minimise your tax bill, get professional advice to find out what expenses, allowances and reliefs you can claim.

Information you’ll need when registering for Self Assessment

If you need to complete and file a tax return and didn’t send one last year, you’ll need to register for Self Assessment. There are different ways to register, determined by whether you’re self-employed, not self-employed or registering as a partner in an ordinary partnership.

If you’re self-employed or soon planning to become a sole trader, you can register online. It’s a simple and relatively quick process, during which you’ll be asked to input your:

  • National Insurance number
  • full name (and any previous names)
  • current address (and when you moved in)
  • date of birth
  • gender
  • phone number
  • email address
  • whether you’ve registered previously for Self Assessment.

You will also be asked basic information about your new sole trader business.    After you’ve completed the questions, HMRC will create your account. You’ll then receive a letter with your Unique Taxpayer Reference (UTR) number within 10 days (21 if you’re based overseas). You’ll need your UTR to file your Self Assessment tax return. You’ll then receive another letter with an account activation code. Once activated, you can file your tax return at any time before the deadline.

Need to know! If you’ve filed a return online previously, but now plan to do something different, you can use the CWF1 form to re-register online, but you’ll need your UTR number. Our blog post, a Guide to UTR Numbers explains more

When to register for Self Assessment

If you’re starting out in self-employment, you should let HMRC know straight away by registering for Self Assessment, but you cannot register if you’re not starting your sole trader business within 28 days.

You must register by 5 October after the end of the tax year where you are required to file a tax return. So, for example, if you need to file for the 2021/22 tax year, you should register by 5 October 2022. If you become self employed in the 2022/23 tax year, you should register by 5 October 2023. If you miss this deadline, you could face having to pay a penalty.

Register if you’re not self-employed

If you’ve filed online before, you can sign into your existing account using your Government Gateway user ID and password.

Need to know! The government plans to introduce Making Tax Digital (MTD) for Income Tax by 2026. Then you’ll need to use digital record-keeping tools and submit records of your earnings and costs every quarter using MTD-compatible software. The current system of filing a Self Assessment tax return will soon come to an end.

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Blog content is for information purposes and over time may become outdated, although we do strive to keep it current. It's written to help you understand your Tax's and is not to be relied upon as professional accounting, tax and legal advice due to differences in everyone's circumstances. For additional help please contact our support team or HMRC.

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