During the first year for which a capital value must be determined for a property or in which new circumstances arise which are of significance to the capital value determination (e.g. new-build, extension, etc.), the taxpayer concerned must provide the tax authorities with sufficient information concerning the property to enable the correct estimated market value and capital value to be calculated; see more about this here. The capital value will subsequently be adjusted automatically in line with price changes for residential properties, and the calculated capital value will be shown in your pre-completed tax return. The area factor in the formula is structured so that the first square metre has a greater value than the next one. For example, increasing the size of a property by 10 square metres from 50 to 60 square metres will have more impact on the value of the property than increasing it from 200 to 210 square metres.