Thousands of householders who have paid the Household Charge have received warning letters on non-payment in error.
The chief executive of the Local Government Management Agency urged people who have received such letters to make contact with the agency.
Speaking on RTÉ's Morning Ireland, Paul McSweeney said if householders do not notify the agency, they will receive a second letter and "technically" could face a penalty.
A batch of warning letters was sent to householders, believed not to have paid the charge, last week.
The letter informed householders that they faced a payment of €127, which included the charge, penalties and interest.
It has since emerged that a number of householders who received the letter had actually paid the charge.
Mr McSweeney said that could be in the "tens of thousands".
He said problems had arisen as a result of a data matching exercise carried out by the agency in an effort to identify those who had not yet paid the charge.
However, he said because of the ways names and addresses were entered, some householders may have received a letter in error.
He said there were cases of spelling mistakes and where people do not use their post code.
"There are also cases where the address that people use themselves is completely different to the address that is registered," he said.
"They spell it differently, the house number has changed or there is a post code that is registered in the property registration authority but which the individual themselves doesn't use.
"What we are attempting to do is try and find out those who have not paid and because we are taking data sets that were never intended to be matched and are trying to use those as a method of creating a property database, these things are unfortunately happening."