Hundreds of homeowners have had their monthly mortgage repayments calculated incorrectly by the largest credit servicing firm in the State.
Pepper Asset Servicing has admitted that some people have been charged too much on their mortgages, with others charged too little. Customers have also been issued with incorrect mortgage statements.
The issues have been brought to the attention of the Central Bank, which said it expects higher standards.
Shannon-based Pepper services some 50,000 residential mortgages on behalf of vulture funds and other unregulated investors.
Pepper services mortgages originated by GE Money, Danske Bank, Bank of Scotland (Ireland), and Irish Nationwide.
It could end up servicing even more mortgages, with controversial loan sales planned by Permanent TSB, AIB, Ulster Bank and the old Bank of Scotland (Ireland).
Pepper said some of the mortgage accounts it services had funds incorrectly credited to them which would now be returned with interest.
It said around 800 customers had been affected by mortgage over-payments, under-payments and by the issuing of inaccurate mortgage statements. The issues affect both residential and commercial mortgages.
It claimed the average amount of over-payments was €100 per customer, with around 400 accounts affected by over-payments.
Pepper will now write to the customers affected.
The problems were exposed last week on the Askaboutmoney.com website run by consumer advocate Brendan Burgess. He said he found it strange that loan-servicing specialists like Pepper had been so slow to contact customers about its errors.
The delay in telling customers about the problems led some people to fear it was a new tracker-like over-charging scandal, Mr Burgess said.
Customers were still not getting answers when they contacted Pepper to get mortgage statements, he added.