Eoin Ó Broin (Dublin Mid West, Sinn Fein) | Oireachtas source

To clarify, at the point of establishing the register, there will be an existing-use valuation and a market valuation based on the existing use and the market value at the point at which the land was last zoned, which will have been in the most recent round of development plans. If there was a piece of land that, prior to that zoning, was agricultural use but was then zoned for residential but which was still being used as agricultural land notwithstanding the residential zoned land tax, the valuation on that land and its existing-use value would be agriculture and its market value would be residential.