(1) Subject to this Part, diesel subsidy is payable to a registered diesel supplier in relation to the sale of diesel by the supplier where—
(a) the diesel is sold to a certified diesel user; and
(b) duty has been paid for that sale under a Commonwealth tax law.
(2) Diesel subsidy is not payable in respect of the sale of a product prepared by a mixture of diesel on which such Commonwealth duty has been paid with any substance on which such duty has not been paid.