They have less than a month to complete their return before the 31 January 2019 deadline or face fines. Around half have already filed their return and HMRC expects the vast majority of taxpayers to complete their returns and pay any tax owed by the end of the month.

The majority complete their returns online – 88% of the total returns filed.

People need to complete a tax return if they:

– earned more than £2,500 from renting out property
– or their partner received Child Benefit and either of them had an annual income of more than £50,000
– received more than £2,500 in other untaxed income, for example from tips or commission
– are self-employed sole traders
– are employees claiming expenses in excess of £2,500
– have an annual income over £100,000
– earned income from abroad that they need to pay tax on

The penalties for late tax returns are an initial £100 fixed penalty, which applies even if there is no tax to pay, or if the tax due is paid on time. This ramps up after 3 months, when additional daily penalties of £10 per day become payable, up to a maximum of £900. After 6 months, a further penalty of 5% of the tax due or £300, whichever is greater and after 12 months, another 5% or £300 charge is due, whichever is greater.

There are also additional penalties for paying late of 5% of the tax unpaid at 30 days, 6 months and 12 months. This could be deducted from your wages if you are a salaried employee.

Many landlords filling out their tax returns this year will start to realise the effect of new mortgage relief tax rules which are currently being phased in. In the tax year 2017 to 2018, only 75% of finance costs – such as mortgage interest – can be deducted from income, and the remaining 25% is available as a basic rate tax reduction. By 2020 to 2021, all finance costs will be limited to the basic tax rate reduction.

Angela MacDonald, HMRC’s director general for customer services, said: “The self assessment deadline on 31 January is fast approaching, but there is still time for customers to file their tax returns online and on time to avoid any unnecessary penalties.

“If you are completing self assessment for the first time or are yet to start your 2017 to 2018 tax return, there is a wide range of support and guidance available on GOV.UK to help at every stage of the tax return process.”