A garda investigation is under way into alleged attempts to use the credit card details of some callers to the Local Property Tax helpline.
The Revenue Commissioners, which is administering and collecting the tax, has confirmed that it is treating the matter as attempted fraud.
An employee of Abtran, the company which handles the call centre for the property tax, has been suspended.
In a statement, Revenue said it understands that details in relation to 11 credit cards were improperly obtained by an unauthorised employee but no cardholder had suffered any loss.
It said the matter has been reported to the office of the Data Protection Commissioner.
Revenue established a telephone helpline when it announced details of how it planned to administer the Local Property Tax in March.
The contract to operate the helpline was won by a Cork-based call centre company, Abtran, which staffed it with 250 of its 1,100 employees.
Abtran was alerted by a caller to the helpline who became suspicious.
Gardaí have alerted the credit card companies involved, and contact is being made with the cardholders involved.
Revenue will operate its own helpline for people with concerns from 9am tomorrow morning on 1890-226-336.
Abtran says it is satisfied that the activity was isolated to just one employee over a short period of time, and nothing like this has happened in the company's 16-year history.