Leading lender EBS has written to 16,000 mortgage holders to apologise after mistakenly reporting them to the Irish Credit Bureau for missing payments.
The lender, part of the AIB Group, says it has now corrected the mistake.
EBS advised the mortgage holders to contact it if they are refused credit. It is the latest mistake to hit what some claim are accident-prone lenders.
In the letter, EBS mortgage holders are told: "We are writing to let you know that we made a mistake on your mortgage account, in that we reported repayments on your account as a missed repayment to the Irish Credit Bureau (ICB)."
It also apologises.
The letter explains that mortgage repayments were made within the first six days of the month, but not on the last working day of the month.
This prompted the lender to report the repayment as having been missed.
"However, we now believe this was unfair to you at that time, to report this as a missed payment to the ICB," the letter states.
EBS said 16,000 letters were sent.
In a statement, it said: "EBS has recently written to some customers regarding a mistake we made which resulted in an amendment to their Irish Credit Bureau (ICB) record.
"The issue impacted a group of accounts where the customers did not make their mortgage payment within the calendar month it was due, but paid it within the first six days of the following month. A missed repayment was reported to the ICB."
The lender said it now believed it had been unfair to report these payments as missed at that time.
"We have apologised to customers for this and have taken steps to prevent this from happening again."
The issue didn't have an impact on the Central Bank's new official Central Credit Register. It was just reported to the Irish Credit Bureau, which is owned by the banks.
The Central Bank has been told about the error, but no compensation is being paid to the customers.
Former building society EBS was absorbed into the much larger AIB group at the height of the financial crisis as part of the rescue plan that involved almost €22bn in public bailout cash for AIB.