Taxback.com is urging former Ulster Bank and KBC Bank Ireland customers to immediately update their new bank account details with Revenue.
It warned that otherwise Revenue is unlikely to receive any tax payment owed to it and taxpayers due a refund may be unable to get their tax rebate either.
People and businesses run the risk of a tax penalty if their tax payment does not get across to Revenue because they failed to update their bank account details on time, Marian Ryan, consumer tax manager with Taxback.com, cautioned.
"When updating your bank account details with Revenue, be sure to update your bank details separately for both tax payments and tax refunds," she urged.
Ulster Bank started to freeze thousands of current accounts last Friday.
Marian Ryan said that in the event of people running into delays changing their Ulster Bank account, or who have trouble accessing their money because the Ulster Bank account has been frozen, they should get in touch with Revenue immediately and outline the difficulties.
"Revenue has said that it will work with taxpayers or their agents to address such matters on a case-by-case basis," she said.
"The same applies to others who may have recently changed their bank – but have not yet got around to updating their bank account details with Revenue," she added.
Taxback.com also said today that self-assessed taxpayers who have missed the November 16 deadline to file their tax return online could still save themselves hundreds - perhaps thousands - of euro, in tax penalties by filing their return by the end of the year.
Almost 830,000 taxpayers are expected to file a self-assessed tax return this year.
Based on the most recent figures from the Revenue, 8% of these may have missed the deadline, which amounts to more than 60,000 people.
"The surcharge faced by late filers can be halved if they file their return within two months of the filing deadline," Ms Marian Ryan said.
"That surcharge increases from 5% of the amount of tax due to 10% of the tax due if the tax return is filed more than two months after the deadline," she said.
"This means a taxpayer with a tax liability of €10,000 could reduce their potential surcharge from €1,000 to €500 if they file their return within two months of the deadline, rather than two months after it," she added.
As Revenue can also charge daily interest on any overdue tax, the amount of potential interest faced by late filers can also be reduced if they file within two months of the deadline.
The tax experts contend that more people are at risk of being late filing their tax return this year – which is for the tax year 2021 - due to the huge growth in the numbers of self-assessed taxpayers.
"The number of people who are filing a self-assessed tax return has grown by almost 120,000 over the last five years," Ms Ryan said.
"In 2021, there were 829,859 taxpayers registered for self-assessment in Ireland, up from 811,772 in 2020 and up from 710,157 in 2017," she added.
