National Irish Bank has reported an operating loss of €8m for the nine months to the end of September.
This compares to operating profits of €32m the same time last year.
Costs rose by 44% to €102m due to the expenses associated with the reorganisation of the bank's retail business announced in June.
The bank said then that it would cut more than 100 jobs and close its network of 27 branches nationwide. Customers will be served through nine 'personal banking centres'.
The 27 branches will close on November 15.
The bank, which is owned by Danske Bank, said it was putting aside €578m for loan impairment charges, down 9% on the same time last year.
But the bank said the quality of its €3.2 billion mortgage load book remained ''satisfactory''.
The bank's country manager, Terry Browne, said its performance during the first nine months of the year was in line with expectations, given the challenging economic conditions.
''Impairment levels remain high, but are lower than in previous quarters this year and remain concentrated in our commercial property book,'' he added.
National Irish Bank is in the process of changing its name to that of its parent group Danske Bank.
Danske said its pre-tax profits for the nine month period jumped 76% to €847m from €482m. The bank's profits, before impairment charges, rose by 35% to €2.176 billion from €1.611 billion the same time last year.
But its loan impairment charges rose to €1.329 billion from €1.128 billion.