The Revenue's online guide to property values has been branded as "misleading and vague".
The website, which was launched over the weekend, is intended to give homeowners a rough estimate of their property tax liability.
The calculator values property according to three basic criteria - property type, location and whether the property was built before 2000.
Several property experts, however, said the estimates bore little or no relation to the current market values of houses as the evaluation criteria were “too vague” or “too general”.
Property economist with Daft.ie Ronan Lyons said the calculations left out a large number of factors which affect the value of a property.
“They’re trying to using house type – detached, semi-detached, terraced - as a way of capturing size but we know these properties can vary substantially.”
"They don't have key information for example the number of bedrooms for every property in the country or the square meterage.”
“That presents a number of issues not just in Dublin where values can vary hugely in a short distance but also in other parts of the country," he said.
Houses for sale in the Sallynoggin area of south Dublin, for example, averaging €239,500, according to Daft.ie, are worth €450,000 — €500,000 based on Revenues estimates which is a difference of €450 per annum in property tax.
Fianna Fail’s local area representative for Dun Laoghaire described the Revenue’s estimates as “incorrect, misleading and damaging”.
He claimed that current market values for a significant number of properties in the Dun Laoghaire area were “nowhere near the rates” the Revenue was estimating.
“Revenue has based property values on electoral divisions which is no way indicative of current market values.”
The Revenue acknowledged its calculator was not entirely accurate in all cases and homeowners would be able to appeal a valuation.
A spokeswoman said the the agency was not in the business of valuing properties.
“We don’t know your house - what size it is or what condition it’s in. We are providing guidance to assist property owners in self-assessing the value of their property.”
She said the Revenuefavours taking factors such as the number of bedrooms or the square footag e into consideration but there was no database in existence which contained that information.
In another example of the site’s valuations, terraced houses built before 2000 on the north side of Clonliffe Road in Dublin appeared in valuation band four, valuing them at between €200,00- €250,000, while similar houses on the other side of the street were listed in valuation band three, valuing them at between €150,000 -€200,000.
The anomaly stems from the fact that Cloniffe Road straddles two electoral wards.
The Society of Chartered Surveyors Ireland (SCSI) urged homeowners to ensure that they are fully informed when self-assessing the value of their home.
SCSI president Roland O’Connell said homeowners would be “foolhardy” to rely solely on the Revenue’s website when calculating their own liability.
“The property valuation determined now will be used for the next three years so it is very important that homeowners, who choose to self-assess the value of their homes, do so diligently and comprehensively to avoid any penalties” he said.
Property website MyHome.ie today unveiled its own property tax calculator which allows users to select a range of recently sold properties and “for sale” properties f rom their area before calculating their liability.
People will begin to receive letters detailing the amount of property tax owed this week.
