The 5 October deadline is for those who are new to self-assessment for the 2022/23 tax year.

Anyone who has an income that they have not already paid UK tax on will need to register, HMRC said. This covers a wide-range of people, from those who are newly self-employed to new landlords who have started renting out property.

Parents who earn more than £50,000 and receive child benefit may also need to fill out a self-assessment tax return, although this system is due to change soon.

If you’re not sure whether you should be registering for a self-assessment tax return, there is a free tool on the HMRC website to check.

You can register for self-assessment on the Gov.uk website. Once registered, a Unique Taxpayer Reference is created, which needs to be entered on the self-assessment tax return.

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Paper returns must be filed by 31 October

The deadline for filing the tax return online, and paying any tax due for the 2022/23 year, is 31 January 2024. If you complete a paper return, the deadline is 31 October.

Last year more than 45,000 people set up a payment plan, with 6% interest, because they weren’t able to pay their self-assessment bill in January. As the Bank of England base rate has risen, the interest on the payment plan currently stands at 7.75%.

Myrtle Lloyd, HMRC’s director general for customer services, said: “If you are new to self-assessment and unsure how the process works – HMRC is here to help.

“We have a wealth of resources and guidance available on GOV.UK to help customers register, sign up to the online services and complete their tax return. We want to help customers get their tax right first time, just search ‘Self Assessment’ on GOV.UK to find out more.”