The Office of the Revenue Commissioners has told over 50,000 property owners that they will begin telling employers and pension providers to deduct the Local Property Tax from non-payers at source unless it is paid within seven days.
In a statement, Revenue said the returns had to be filed online within one week.
It also said this morning that to date over 1.58 million returns have been filed and over €175m has been collected from the tax.
Revenue said any householders with questions can contact the LPT helpline on 1890200255.
Speaking on RTÉ Radio, Revenue spokeswoman Vivienne Dempsey said the letters should not be ignored.