That's because the regulator's reimbursement terms for banks that fleeced customers for a pound here or a penny there in the late 1980s and early '90s require that the offending institutions not benefit from any money which cannot be repaid.

Instead, they must give it to charity.

It's not easy to track down exactly who got ripped off 15 years ago, which means a substantial portion of the 167m in overcharged fees will go unclaimed, creating a tidy windfall for the non-profit organisations.

To take the most egregious violator as an example, AIB was stung for 31.6m in repayments in 2006 relating to the application of incorrect (but favourable to the bank) margins on foreign exchange transactions in the 1990s and other, earlier overcharging instances. However, only 11m of that went to customers. Nearly twice as much . . . 20.6m . . . was passed to charity. If that proportion applies across the banking industry, customers will get 58.5m back while charities will benefit to the tune of 108.5m.

The problem, as a spokeswoman for the regulator explained to the Sunday Tribune, is that most of the transactions in question occurred across a counter in a branch many years ago, leaving no identifiable trace apart from the amounts involved. Someone who changed dollars for punts in 1992 wouldn't have left a name, address or telephone number. So the banks aren't really in a position to make proper restitution. And since they can't just keep their ill-gotten gains, they're doing the next best thing: giving them to worthy causes.

Whether the great number of unidentified out-of-pocket customers would have chosen the charitable route for their surplus funds is unknown, but it's likely they would think twice before asking a bank to administer the transaction. If, as Merrill Lynch opined last week, AIB really is on the block, maybe the new owners might try more conventional means of facilitating philanthropy.