Halifax customers who have not switched or closed their current or credit card accounts before this evening's deadline have had their cards and accounts deactivated.
Some 21 Halifax branches are to close today, with the remaining 23 closing next Wednesday.
In February, Halifax, which is owned by Bank of Scotland (Ireland) announced its plans to close its 44 retail branches with the loss of 750 jobs.
The bank has an estimated 50,000 current account and 50,000 credit card customers.
Halifax's website was deactivated from this 5pm evening and customers are being redirected to www.bankofscotland.ie
The bank has also stopped taking on new mortgage customers, though current mortgage holders can retain their mortgages with the bank.
Halifax was criticised in recent months by consumer groups for offering mortgage customers €1,000 to switch mortgages to other providers. The vast majority of the bank's mortgage customers have tracker mortgages. A spokeswoman for Halifax said yesterday that the majority of mortgage holders have remained with the bank.
Halifax, which holds about 7 per cent of the mortgage market, introduced tracker mortgages to the Irish market, driving down the cost of home loans and profit margins.