Ulster Bank has announced it will be selling 6,500 Irish mortgages in arrears which have a face value of €1.6bn.
Almost half of these, 3,600, are owner occupied-loans and another 2,900 are buy-to-let investor loans.
On average, the loans are in more than three years in arrears. Customers will not be informed that their loans are sold until a buyer has been found by the bank.
It is possible that these loans will be sold to so-called "vulture funds".
Ulster Bank is reported to have set aside €119m for the loss that will be incurred by the sale.
In a statement, the bank said: "This difficult decision comes a decade after the financial crisis began and the continued forbearance cannot be maintained.
"Not all mortgages are sustainable and we are obliged to reduce the level of non-performing loans."
Approximately 17% of the bank's loans are non-performing, and it is under pressure to cut this to 5% in the coming years.