ULSTER Bank's customers are urged to keep detailed records of how the technical fiasco affected them.
The embarrassing glitch which has caused chaos for tens of thousands is likely to stretch to the end of the week.
Ulster Bank acknowledged the "unprecedented" problem was causing an "unacceptable inconvenience".
The IT issue plaguing the bank has now rolled into its sixth day and shows no signs of being resolved today.
The issue continued to spark anger this morning with customers apparently unable to access internet banking.
Professor of accounting at UCD Smurfit School of Business, Eamonn Walsh has urged consumers to keep details of the failure for fear that it could cause problems down the line with credit ratings.
"Customers should keep a written record of how they have been affected by this," he said.
"Rather than people trying to remember what occurred, it is better to write everything down with supporting documents."
AIB stepped in and began processing payments on Friday after the Irish Payment Services Organisation held crisis meetings. But Ulster Bank said this morning that the build-up of interrupted transactions was taking "significantly longer" than expected.
A spokeswoman for the bank said that staff were "working around the clock" to resolve the problems.
Last week the issue mainly affected those paid weekly or with one-off transactions.
But this is the last week in the month -- a key monthly payment period for thousands of employees across the country.
Ulster Bank is under pressure to solve the issue before the end of the week and branches will have extended opening hours again today until 6pm.
Payments from Ulster Bank into other banks are said to be nearly cleared but a major issue remains with updating the bank's own accounts processing incoming payments and updating. More than 110,000 transactions with a value of €500m were processed over the weekend, and most payments involving customers from other banks had now been processed.
Customers can continue to access cash through the bank's ATM network, a spokeswoman said, and can take out withdrawals if they bring their account details and ID with them to a branch.
The original IT problem was caused by a software upgrade to the payment processing system which was corrupted. This problem has now been fixed and staff have been working through unprocessed transactions.
Ulster Bank's helpline number received almost 9,000 customer telephone calls over the weekend, while 11,100 people called into its branches.
Fianna Fail Justice Spokesperson Dara Calleary slammed the Central Bank's low key response to the matter.
"The Central Bank has a responsibility to ensure that payments systems are safe and protected," he said.