How do I fill in a CIS Tax Return?

Tax time can be a source of great stress for the self-employed. If you’re confused by your self-assessment tax return, we’ve broken it down to make the process as easy as possible for you. Read on to find out more.

Will I need to submit a tax return?

If you’re self-employed or you’re a member of the Construction Industry Scheme, it’s likely that you will need to submit a tax return to disclose your earnings for the financial year. Usually, HMRC will contact you to remind you that this is due. If you haven’t heard anything, you can check your eligibility online.

What will this entail?

You will firstly need to register for a self-assessment tax return using HMRC’s online portal. Once registered, you will need to complete an SA100 form.

What information do I need to prepare beforehand?

In order to complete your tax return, you’ll also need your UTR (Unique Tax Reference).

This number is unique to you and will be assigned once you register your company. This ten-digit number is how HMRC determines that you are self-employed.

You may also need to complete the following:


You will need to include your turnover for the financial year. This is calculated by totalling up your sales. You must also declare any additional income and property income if applicable.


You may be able to claim tax relief on any losses you have incurred in the financial year.  The amount of tax relief you can claim against your income each year is limited to the greater sum of £50,000 or 25% of your adjusted total income.

Interest earned

This includes any interest gain from your bank accounts and payment deductions from contractors. This is only applicable if you are a subcontractor. You should add up all of the deductions made by contractors from the financial year, you will find the deductions on the statements given to you by contractors.

Business expenses

Any expenses used for the purpose of your business should be declared to HMRC.

Here at Barron & Co, we understand that filling out a CIS self-assessment form can be tricky. However, if you are based in Birmingham why not trust our chartered accountants to prioritise your best interests while doing all the hard work. Get in touch on 0121 426 4155 to discuss your needs directly with our CIS tax returns accountants or visit our website.