The ACT Security of Payment Act provides for interest at s13(2) of the Act as follows:

(2) Interest is payable on the unpaid amount of a progress payment that is payable under subsection (1) at the greater of the following:

(a) the rate of interest applying from time to time under the Court Procedures Rules 2006 , schedule 2, part 2.2 (Interest after judgment);

(b) the rate stated underthe construction contract

ACT practitioners should note that the Court Procedures Rules 2006 can be found here at this link