Ulster Bank is set to inform tens of thousands of current and former mortgage holders about a system error that may have affected their interest payments and repayment schedules. While the bank claims the impact is minimal for most, some customers experienced up to two months of distortion in their repayment terms. The average additional interest impact is approximately €50. The bank is currently reviewing up to 90,000 impacted mortgages and will communicate with affected customers in the coming months.