National Irish Bank closed its 27 branches around the country and rebranded as Danske Bank today.
NIB customers will now have to use post offices, phone or internet banking, or use one of the bank's new small advisory centres to conduct their banking business.
About 100 staff are leaving under a voluntary redundancy scheme because of the branch closures.
Danske Bank Advisory Centres will be open in nine locations next week where customers can meet advisors face-to-face.
These will be located in Waterford, Athlone, Cork, Limerick, Letterkenny and across Dublin in the IFSC, Tallaght, Swords and Stillorgan.
The head of the Credit Review Office, John Trethowan, said that the physical presence of banks has a lot to do with lending to business.
Branch closures can make whole business communities feel remote and isolated, he said.
He said that loan applications are not now dealt with locally, but at a central office in Dublin, and he said people do not like that.
"With physical locations contracting as banks reduce their cost base, there's more to be done by banks when thinking about how they interface with customers."
As well as NIB's 27 branch closures today, last month AIB closed 44 branches out of a total of 67 marked for closure this year.
Bank of Ireland recently closed a landmark branch in Limerick city, and is slashing services at 40 branches, instead of closing them.
Permanent TSB will close up to 19 branches out of a total of 92. Ulster Bank is expected to close up to 40 of its branches next year. EBS, which is now part of AIB, is also expected to close a number of branches.