As many as 80,000 bank customers are expected to receive letters warning of a possible Revenue inquiry into their offshore accounts or investments over coming days, according to industry sources.
It is believed the bulk of the letters will be sent to customers of AIB and Bank of Ireland who have held accounts with branches in Northern Ireland but had addresses in the State.
A small number of letters will also be sent to customers with accounts in branches of Irish banks in Jersey and Britain.
Ten finance financial institutions - many with significant offshore operations - will be sending letters to their customers, following a meeting between their chief executives and the Revenue late last year.
The customers will be told that they face a Revenue inquiry into their tax affairs and will be advised to take advice on the issue.
If a tax problem emerges, the customers concerned will have just five weeks to regularise their position if they want to avoid the possibility of heavy financial penalties.
If they do not present themselves, the customers will face the prospect of their records becoming available to the Revenue under new powers, introduced in the Finance Bill, allowing Commissioners to apply to the courts to view records held by offshore subsidiaries of Irish financial institutions.
The Revenue has reported a very high level of queries in relation to offshore accounts since its new investigation was made public on Thursday.
Neither of the two main banks was in a position to specify how many letters their offshore branches would be sending in connection with the matter yesterday, but sources believe that each will be contacting tens of thousands of customers.
Smaller banks will also be involved in the process but to a more limited extent. Permanent TSB (formerly Irish Permanent), for example, is thought to be contacting no more than 200 customers of its branch in the North.
It emerged yesterday that the Revenue Commissioners had collected "tens of millions" of euros from Irish-resident customers of Irish Permanent in the Isle of Man through an inquiry launched last year.
Permanent TSB issued some 3,000 letters to customers in connection with that investigation but it is not known how many customers have since settled with the Revenue. A similar examination of accounts held in the Bank of Ireland Trust Company in Jersey led to the Revenue netting some €105 million in tax and penalties from 254 individuals.
The Revenue has since estimated that some 80 per cent of Irish residents who had settled trusts with Bank of Ireland in Jersey came forward voluntarily after receiving letters.
