Calculate the deduction separately for each part of capital works that meets the description of your area.
Multiply your 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 the fund 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. See section 43-215 of the ITAA 1997.
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.