Easy guide to completing your self-assessment tax return


If you have never filled in a self-assessment tax return before, it can seem very daunting. However, once you understand the process, it is relatively simple, if you have all the information you need to hand.

Follow our handy guide below to make it easier for you or get in touch with us today and we will be happy to assist


If you are filing a self-assessment tax return for the first time, you will need to register with HMRC. You can do this online via HMRC’s website. The process will vary depending on whether you are self-employed, registering a partnership, or not self-employed so you need to select the option that applies to you.


As soon as you register for self-assessment or set up a limited company, you will automatically be issued a UTR number. If you have misplaced it, you can also call HMRC on 0300 200 3310 and they will be able to assist. You will be prompted to answer some security questions. such as your personal details and you will also need your National Insurance number to hand.

If you want to submit your Self-Assessment tax return online, you will also have to set up a Government Gateway account. To do this you need to go to this link – HMRC services: sign in or register – GOV.UK (www.gov.uk) and follow the instructions.

Once you’ve set-up the account, an activation code will be emailed to you. This will complete the set-up of your Gateway account. 


Before you start, you will need to make sure you have gathered the following information:

  • your 10-digit Unique Taxpayer Reference (UTR)
  • your National Insurance number
  • details of your untaxed income from the tax year, including income from self-employment, dividends and interest on shares
  • records of any expenses relating to self-employment
  • any contributions to charity or pensions which might be eligible for tax relief
  • P60 or other records showing how much income you received which you’ve already paid tax on.

The above information should only refer to the previous tax year – so the 6th April of the previous year to the 5th April of the current year.


You will only need to fill out the sections that are relevant to you. Leave anything else blank.


It is important to take your time and fill in your tax return carefully, making sure the details are correct as you go. If you are doing this online, you do have the option to save it and come back to it so there is no need to rush. 

You should check back through all the information you have entered before you press “Submit”.

Once you have submitted, you should see confirmation that you have submitted your self-assessment along with a code number. It is advisable to keep a record of this number as a reference for the future. 

The amount you owe will be calculated immediately after you submit your tax return. It is vital that you pay it before the deadline to avoid a penalty. The deadlines for paying your tax bill are usually:


You should always try to keep a record of your returns. If HMRC chooses to investigate your tax return, you will need to provide your receipts, bank statements etc as proof.


We hope this guide will help you to understand your Self-Assessment Tax Return, but it can be a complicated process and easy to overlook something that would save you paying more tax than you need to. 

If you would like us to submit your Self-Assessment Tax Return on your behalf, then we can take care of the whole process for you and keep you updated and informed along the way.

If you need any help, please do not hesitate to contact us or drop us an email to – marketing@bluespiregroup.com 

Picture of James


Director, Blue Spire.

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