The Revenue Commissioners has said that several thousand homeowners - liable for Property Tax - will not receive letters.
The target of over 1.6 million letters have now all been sent to properties around the country.
However due to errors in the computer system - people who have not received one - must make contact with Revenue.
New figures show that 219,000 households have registered for the tax - with €1.3m so far collected.
The Revenue Chairperson Josephine Feehily said that 12.5% of the expected returns have been filed.
"The first LPT receipts have been credited to the exchequer, and with five weeks to go to the online filing deadline more 218,903 LPT returns have been received by Revenue to date," she said.
"However it is important that I take this opportunity to remind property owners that they are liable for local property tax even if revenue hasn't contacted them."