Calculate the deduction separately for each part that meets the description of your area.
Multiply the construction expenditure by the applicable rate (either 4% if the capital works began after 21 August 1984 and before 16 September 1987 or 2.5% in any other case) and by the number of days in the income year in which you owned, leased or held your area and used it in a relevant way. Divide that amount by the number of days in the income year.
Apportion the amount if your area is used only partly to produce assessable income.
The amount the fund claims cannot exceed the undeducted construction expenditure.