(1) In section 10(b) of the Principal Act—
(a) in sub-paragraph (i), after "carried out" insert "or undertaken to be carried out";
(b) in sub-paragraph (ii), after "supplied" insert "or undertaken to be supplied".
(2) At the end of section 10 of the Principal Act insert —
"(2) Despite sub-section (1) and anything to the contrary in the construction contract, a claimable variation may be taken into account in calculating the amount of a progress payment to which a person is entitled in respect of that construction contract.
(3) Despite sub-section (1) and anything to the contrary in the construction contract, an excluded amount must not be taken into account in calculating the amount of a progress payment to which a person is entitled in respect of that construction contract.".