A spokesperson for Irish Water has said that she doesn't know how much public money was lost in the PPS number debacle.
Irish Water's Elizabeth Arnett says the utility is currently destroying the numbers it received and that process could be completed by the end of the month.
The PPS requirement was scrapped by the Environment Minister in November after a public backlash over privacy concerns.
Ms Arnett said that the company still cannot say how much it has cost the taxpayer.
"I don't have a precise figure in relation to that, but I can certainly look at it and see," she said.
She added: "The remaining PPS numbers that are on recordings, we are looking at a process as to how we would delete those that would be satisfactory to the Data Protection Commissioner.
"So we're well advanced in terms of that."