The Central Bank has fined Ulster Bank Ireland almost €38m for dozens of regulatory breaches in its handling of its tracker mortgage customers.
The fine is the largest ever levied against any firm by the regulator.
During its enforcement investigation, the Central Bank uncovered what it described as "serious failings" by Ulster Bank in its treatment of 5,940 customers over a 16 year period form 2004 until last year.
In total, Ulster Bank has admitted to 49 separate regulatory breaches.
Its actions, the Central Bank found, caused avoidable and unacceptable harm, including extended periods of overcharging and the loss of 43 customers' properties, including 29 family homes.
"Our investigation identified the numerous opportunities that UBID had to do right by its customers and the efforts that UBID went to in order to evade its obligations to these customers," the Central Bank's Director of Enforcement and Anti -Money Laundering Seána Cunningham said.
"Despite it being clear to UBID from customer complaints that certain customers were paying more for their mortgage than they should be, UBID continued to deny customers the lower tracker rates that they were entitled to," she stated.
Tracker mortgages use an interest rate that tracks the main European Central Bank rate.
Ulster Bank introduced tracker mortgages in 2001, but like other banks withdrew them in 2008 when the financial crisis hit and made them more costly.
The Central Bank said that Ulster Bank had failed to disclose to impacted tracker customers all the consequences of fixing their interest rates.
It also devised and implemented a deliberate strategy not to provide certain customers with their correct tracker mortgage entitlement, unless they complained.
The bank also did not adequately implement a principle known as "Stop the Harm", which would have protected all potentially impacted tracker customers from further detriment, the Central Bank said.
Ulster Bank also failed to make sure its operational systems and controls were sufficient to ensure that its customers were provided with their correct tracker mortgage entitlements.
The Central Bank also found Ulster Bank devised and sought to implement a campaign to encourage certain tracker customers to convert their tracker rates to fixed rates during 2008, without telling them that they would not be entitled return to their original rate if they moved.
Ulster Bank also failed to meet a statutory deadline for the provision of information in the context of the Central Bank's investigation.
"In deciding in 2011 to only return customers who complained to their tracker rates, UBID calculated the cost of returning all impacted customers to their tracker mortgage rate," the Central Bank said.
"Instead, informed by that financial analysis, it decided to take the option that cost it the least and return only customers who complained to their correct rate," it said.
"Having initially provided its customers with unclear information and having failed to warn them of the very real consequences of their mortgage-related decisions, UBID put further impediments in its customers' way," it said.
"The onus was placed on customers to complain,and to do so in a certain way, in order to get what they were entitled to," it added.
The Central Bank fined Ulster Bank nearly €54m, but reduced this by 30% under its settlement discount scheme.
The fine is much larger than the €21m sanction imposed on Permanent TSB in 2019 for similar breaches, and the €18m that KBC Bank Ireland was fined last year following the regulator's probe into its handling of tracker customers.
Ulster Bank has also paid out €128m in redress, compensation and account balance adjustments to customers.
Last month, the bank said it would wind down its operations in the Irish market over the coming years.
The Central Bank's tracker mortgage examination final report concluded in 2019 that 40,100 customers across the main banks had been affected by the controversy, and at that point the lenders had paid out €683m in redress and compensation.
