Taxpayers who have to pay but have not been issued with a tax return must notify HM Revenue & Customs (HMRC) by 5 October 2019 for the 2018/19 tax year if they become chargeable to income tax or capital gains tax.
It is a requirement to notify HMRC within six months of the end of the tax year, which means that the deadline is 5 October.
For taxpayers that are not self-employed, they can make the notification on form SA1, which can either be submitted online or printed and sent via post.
Self-employed taxpayers must also register for Self-Assessment and Class 2 National Insurance contributions (NICs) online via the Gov.UK website.
From 2015/16, Class 2 NICs are payable via the Self-Assessment system, rather than separately.
Once the notification has been submitted, HMRC will issue a tax return, with the deadline for filing this return being depended on the date it was issued.
The notification provisions only apply for taxpayers who have not received a tax return from HMRC, and if they have received a tax return then they can disclose these in the usual manner.