It could be several months before the Minister for Finance, Mr McCreevy learns how much the Exchequer will gain from the windfall that may result from the introduction of the euro and if it can be included in accounts for this year.

The Central Bank has estimated that around 5 per cent of the now defunct Irish currency - around €240 million - will not be returned to it. For every pound issued in the past, the Central Bank must maintain a similar amount as a liability on its balance sheet.

In his Budget speech last December, the Minister said he had requested the Central Bank to transfer the estimated value of unreturned Irish currency to the Exchequer which he included in his Budget for 2002.

"At some stage, we would be writing off a certain amount of that liability. There is no point in keeping it as a permanent liability when the reality is it is never going to come back," said a spokesman for the Bank.

"The Minister was saying, estimate how much it is and effectively give that to him before we write it off."

The Central Bank board said it would consider the request once the euro changeover was complete.However, it has yet to decide on the amount, when it will be written off and whether to give it to the Minister in advance.

"The likelihood is we wouldn't be writing that off until at least some time this year and even into next year and, secondly, even if you write it off this year, that wouldn't accrue to the Exchequer until next year," said the spokesman. A decision may not be made for some months. It is understood the matter has not yet been included on the board's agenda for this month.

The Central Bank's estimate of 5 per cent was based on estimates from other European central banks and on the Irish Bank's own experiences. "We made the point that this was a tentative estimate and we had no real way of knowing for some time until we saw how the pattern of returning cash would go," said the spokesman.

More positively for the Minister, the spokesman said the transfer to the Exchequer of some €370 million in net proceeds from the minting and issuing of coin in the past, which was included in the Minister's Finance Bill, should be straightforward.