The Office of the Revenue Commissioners has warned people who have not received their Local Property Tax Return that they must still file their return.
Speaking on RTÉ's Morning Ireland, Revenue's Property Tax Manager Vivienne Demspey said that the property pin number supplied by Revenue is not necessary to file a return.
She said: "At this stage, if you haven't received a return, go online. The Revenue's website has a Local Property Tax login page. Go on to that page and you can file online.
"There's a special provision there ... 'I have not received a property PIN'.
"Log on to that and in preparation have your PPSN, your valuation, the payment details you want to make and you will be able to make that return literally in a matter of minutes."
Ms Demspey also stressed that Revenue is not in the business of valuing people's homes.
She said the figure provided by it is simply an estimate of the value that Revenue will rely on should a person fail to file a return.
Ms Dempsey said that the onus is on the homeowner to supply an accurate valuation of their home within €50,000.
She said: "What revenue has not done is put a valuation on people's properties. We're not in the valuation business.
"The figure that is on the letter is a notice of estimate and this is the amount the revenue will collect if you do not complete a property tax return."
The deadline for filing postal returns is Tuesday and Revenue said it will accept letters that are posted on Tuesday.
People who opt to file their return online have until 28 May to complete the return electronically.
Revenue said its helpline (1890-200255) is being extended until 8pm this evening and is opening tomorrow to help householders.