As the deadline to register for a self-assessment tax return looms, Britons are being urged to check whether they may now be liable for one.

As a result of rising wages and frozen thresholds, one of the groups “most at risk” is parents who claim child benefit and may have earned over £50,000 for the first time, accountancy and business advisory firm BDO has warned.

Experts at BDO said: “While the Government has announced plans to collect this charge through the tax code system in the future, this is highly unlikely to apply for the 2022/23 tax year, so those affected will need to register for Self Assessment.”

Meanwhile, the cost-of-living crisis has prompted many people to seek alternative sources of income through “side hustles” or freelance work, who will also need to declare extra earnings via a tax return.

If, during the 2022/23 tax year, a person was self-employed as a sole trader and earned more than £1,000; were a partner in a business partnership; had a total taxable income of more than £100,000; or if they met the criteria to pay the High Income Child Benefit Charge, they have until October 5, 2023, to register for Self Assessment if they haven’t done so before.

Dawn Register, head of tax dispute resolution at BDO said: “Because of rising wages and frozen thresholds, many more people will have unwittingly passed the threshold at which they will be required to file a Self Assessment tax return for the first time.

“Although the online deadline for filing a return for the tax year 2022/23 isn’t until January 31, 2024, those who qualify for Self Assessment must register by October 5, 2023.

“One of the groups most at risk is parents who claim child benefit and who may have earned over £50,000 for the first time. They will find they are subject to the High Income Child Benefit Charge and will need to fill in a tax return.

“Those who have sought to supplement their income – for example by renting out property, selling goods online or taking on additional freelance work – may also find they need to register for Self Assessment.”

Ms Register added: “Unfortunately, ignorance is no defence, so it’s important that people register and file on time to avoid late filing penalties.

“Those affected will also need to have the funds available to pay the High Income Child Benefit Charge or any additional tax required by the January 31 deadline or they run the risk of incurring late payment interest.

“This is currently at 7.75 percent, the highest level for 15 years.”

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.”