This factsheet lists the key tax dates in 2018 as they apply to a firm's different tax liabilities. It also provides information about the penalties for non-compliance with the deadlines.

Taxation is a complicated area and professional advice should be sought to ensure that all tax obligations are met.

Income tax (self-assessment)

Anyone who is self-employed or in a partnership is required to complete a self-assessment tax  return each year to determine how much income tax and NI (see later section of this factsheet) they must pay. Company directors and individuals with complicated tax affairs are also required to complete a self-assessment tax return to enable HMRC to assess whether any additional tax is owed. Anyone with an income tax liability of more than £1,000 may be required to pay one half of that liability 'on account' for the following year's tax by 31st January, and a second payment on account by 31st July.

For further information  on completing a Self-Assessment Tax Return go to

31st January 2018
• This is the deadline for submitting an online tax return to HMRC for the tax year that ended on 5th April 2017. The tax return must reach HMRC by midnight on this date to avoid incurring any penalties.

• Anyone who has not submitted their completed tax return by this date will be charged
an automatic penalty of £100. This penalty applies even if they have no tax to pay. For a partnership tax return, there is a £100 penalty for each partner.

• The balancing income tax payment for the year ended 5th April 2017 must be paid by this date.

• In addition, the first payment on account for the current tax year should be sent to HMRC by this date. This should correspond with the expected final liability for the year ending 5th April 2018. If the tax liability is likely to be significantly less than expected, HMRC should be notified and a claim should be made to reduce the payment due.

• This is the deadline for amending a 2015/16 tax return for claims relating to previous tax years. 

28th February 2018
An automatic 5% penalty will be charged by HMRC if the balancing payment has not been made by this date.

6th April 2018
This is the first day of the new tax year (2018/19). HMRC sends 2017/18 self-assessment tax return (SA100) forms or Notices to Complete a Tax Return (SA316) before the end of May.
.... To find out deadline dates for the rest of the year read this guide in full by registering on the Swindon & Wiltshire Growth Hub and download, plus receive future  business updates and information on the latest opportunities including access to funding, B2B events and the latest news.