Revolut is moving its Irish customers users' accounts to Lithuania.
The move by the payment app will be made in December, to coincide with Brexit.
The company is currently licensed in the UK with an electronic money or 'e-money' licence.
However it does not have a banking licence, and has until now been using that same e-money licence to operate in Ireland under EU 'passporting' rules.
This allows a bank or financial institution licensed in one EU country to 'passport' or transfer the licence to another country, without having to get full regulatory approval.
However due to Brexit, Revolut's UK e-money licence will no longer be valid in Ireland at the end of the year.
The firm will therefore transfer its Irish users to its business in Lithuania, where it also has a banking licence.
What is changing?
This means Irish customers will then be regulated by Lithuania's Central Bank, and not by Britain's Financial Conduct Authority (FCA) as is currently the case.
This will see customers' IBAN and BIC numbers change.
This is because all Revolut IBANs currently start with a 'GB' as this is what is used for all UK-based accounts.
This will now change to 'LT'.
For most customers no action will need to be taken.
But those who get their salary paid into their account or have direct debits will need to update their details.
Those getting paid into their account by their employer must let them know that their account details have changed.
Customers must also update any direct debits or standing orders, otherwise they could bounce.
Revolut is working on getting an e-money licence from the Central Bank of Ireland, though no firm timelines have been agreed.
More than four million people now use its services - including some one million Irish users.
It has previously warned customers over the consequences of a potential no-deal Brexit.