The return to full service on Monday follows weeks of frustration for both business and personal customers, as the bank battled through the huge transactions backlog created when over 100,000 customers in Northern Ireland were left unable to access their accounts.

For those customers unhappy about problems they have experienced, there are steps to take.

In the first instance, people should speak to the Ulster Bank but, if they're still not happy, they should contact the Financial Ombudsman.

The Financial Ombudsman recommends keeping detailed records of any out-of-pocket expenditure - including documentation and receipts - and to present this to your bank branch as evidence of your inconvenience.

We are currently consulting with regulators and consumer groups and will be in a position to communicate further details shortly.

Jim Brown, Ulster Bank

As well as any compensation Ulster Bank might offer later this week, the Financial Ombudsman might also instruct Ulster Bank to compensate customers for "distress and inconvenience".

This is a vague term which can cover lots of things. You could argue you are distressed or inconvenienced if a phone line is busy, or your name is spelt incorrectly on a form, but you are unlikely to get compensation for it.

The Financial Ombudsman mostly awards compensation of less than £300 and in only a small number of exceptional cases, it's more than £1,000. Cases involving what the Ombudsman's Office calls "pain and suffering" are likely to lead to higher compensation.

While Ulster Bank has said its systems are now running as normal, a statement added that the "clean-up" operation continues and a small percentage of outstanding transactions are being processed over the next couple of days.

"There is no doubt that there will be reconciliations to some customer accounts that also need to take place over the coming days and weeks," the statement said.

"However, for the majority of customers it is now business as usual."

Technical glitches hit the RBS Group on Tuesday 19 June and affected millions of Ulster Bank, RBS and NatWest customers throughout the UK and Ireland.

RBS and NatWest saw access to their accounts restored almost three weeks ago, but Ulster Bank customers had to wait while the lender battled through an "unprecedented" backlog.

Jim Brown, Ulster Bank Chief Executive, said that fees and charges directly under Ulster Bank's control will be reversed automatically and this process has already begun.

"No customer will be out of pocket as a result of this issue," he added.

"We understand that this issue has caused significant and unacceptable disruption and we are introducing a range of measures to recognise the impact it has had on customers' day-to-day banking needs."

Regarding credit ratings, he said: "We know that this is a significant concern for customers and we are working with the credit reference agencies to ensure that no customer's credit rating is affected as a result of this incident."