A Guide To Self Assessment

Self employed persons are required to complete and return a tax return each year.  The tax return details your income and capital gains (profits on the sale of certain assets) and claims for tax allowances or reliefs.

Tax returns account for the previous year of business, which runs from 6 April – 5 April.

Tax returns may be submitted for part years, for example if you are a new business start up which has been operating for only a portion of the year to date. 

Who needs to complete a self assessment tax return?

If you are self employed or a partner in a business partnership, you need to complete a self assessment tax return each year. 

Even if you aren’t business, or your tax affairs are complex, you may still be required to submit a tax return.  Those in the following categories may also be required to submit a tax return:

• company directors

• trustees

• persons receiving foreign income

How do I get a self assessment tax return?

You must register for self assessment with HM Revenue & Customs (HMRC).  A ten-digit tax reference, called a Unique Taxpayer Reference will be generated and sent to you. This reference must be kept safe and secure. 

HMRC will issue correspondence to you advising you when your tax return is due. This is usually issued in April.  If you don’t receive any correspondence from HMRC, contact them to make them aware. 

Tax returns can be completed on paper or online. Sending online is quick, easy, and allows three months longer to send it.  You must sign up with HMRC for online submissions. 

Do I have to complete the return myself or can I get help?

You may wish to complete the tax return yourself, especially if your business income and expenditure is straightforward and easy.

However, there may be instances where support and guidance is helpful or required to ensure you accurately capture and share all relevant details towards HMRC calculating a correct tax payment.  In this instance, you may nominate an accountant to act on your behalf and submit the tax return to HMRC for you.

What are the submission deadlines and penalties? 

Paper submissions must reach HMRC by midnight on 31 October.

Online tax returns must reach HMRC by midnight on 31 January.

If HMRC does not receive your tax return in time, a penalty will be due.  The later you submit your tax return, the more penalties you will be likely to pay.

Making a tax payment

Tax payment due must be made by midnight on 31 January.

For those who also make payments towards the next tax year, called Payment on Account, those payments are due by 31 July. 

It is recommended to set aside money throughout the year towards your tax bill to avoid incurring any financial shortfalls when the tax payment deadline nears. 

If you no longer need to send a tax return

You must tell HMRC if you believe you no longer need to send a tax return.

If HMRC agrees, they will send a letter confirming you do not need to file a return.

Further information and guidance

More information and guidance, and latest news and updates can be found on the HMRC website.