Section 13 of the Principal Act is amended -

(a) by inserting "(1)" before "The Commissioner", and

(b) by inserting after subsection (1) the following:

"(2) Without prejudice to the generality of subsection (1) or section 19(5), where the Commissioner is satisfied that it is appropriate to do so, the net annual value of particular properties or classes of properties may be determined using general market data, or aggregated data (including data derived from statistical and computer-aided techniques), that are likely to be representative of a particular class of properties.".