The Victorian Security of Payment Act provides for interest at s12(2) of the Act as follows:

(2) Interest is payable on the unpaid amount of aprogress payment that has become due and payable in accordance with subsection (1) at the greater of the following rates —

(a) the rate for the time being fixed under section 2 of the Penalty Interest Rates Act 1983; or

(b) the rate specified under the construction contract.

Victorian practitioners should note that the interest rates can be found at this link Penalty Interest Rates Act 1983 .