Shoppers are being advised that they will have to use their PINs when using their credit cards to make purchases from March.
Chip-and-PIN technology has been introduced on a phased basis in Ireland over the past few years, but consumers have still been allowed to sign for their purchases during the changeover period.
The old method will no longer be available to credit-card holders from March 17, except in limited circumstances.
The anti-fraud measure means the 9% of credit-card holders who are still signing for purchases will not be able to do so after St Patrick's Day.