HM Revenue and Customs ( HMRC ) must receive your tax return and any money you owe by the deadline. The last tax year started on 6 April 2017 and ended on 5 April 2018. There's an additional payment deadline of 31 July if you make advance payments towards your bill (known as 'payments on account').

Self Assessment deadlines in 2018

Before the next online tax return deadline comes around, there are several other 2018 Self Assessment dates to bear in mind. It’s unlikely that all of them will be relevant to you, but understand which ones apply so that you don’t miss any important deadlines.

• 31 July 2018 is the deadline for making your second ‘payment on account’ instalment to HMRC. This will only apply to you if you were self-employed during the tax year 2016-17 and you owed tax of over £1,000 when you submitted your tax return for this period. Take a look at our payment on account guide if you’re not sure.
• 5 October 2018 is the deadline for telling HMRC that you’re self-employed so that they’re aware you need to complete a tax return next year. If you’re already registered as self-employed, there’s no need to do this again. Check out our guide to registering with HMRC for more information.
• 31 October 2018 is the Self Assessment deadline for the tax year 2017-18 if you want to file a paper return rather than filing online. However, most businesses find it easier to file their tax return online - and under the government’s Making Tax Digital plans, filing paper returns may not be an option from April 2020.
• 30 December 2018 is the deadline for filing your online tax return if you want the tax owed to be collected through PAYE via your tax code. This is only an option if you have some income that’s already taxed through PAYE (i.e. you’re employed as well as self-employed), and if your Self Assessment tax bill for 2017-18 is below £3,000. See our article on tax codes for more information.

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