(1)  The Valuer-General may, without causing a fresh valuation to be made of all lands within a valuation district, at any time cause a supplementary valuation of any land to be made for any of the following reasons:

(a) that the land is not included in the valuation then in force;

(b) that the land is of greater or lesser extent than is described in the valuation;

(c) that the land has, since the making of the valuation then in force, become rateable or has become subject to a new or additional rate;

(d) that, by reason of the destruction or removal of buildings or other improvements or of any other cause, the value of the land has been, in the opinion of the Valuer-General, materially decreased;

(e) that, by reason of the erection or construction of buildings or other improvements, the value of the land has, in the opinion of the Valuer-General, been materially increased;

(f) that, in the opinion of the Valuer-General, it is necessary to rectify an error made at the date of the revaluation in respect of values or ownership.

(2)  A supplementary valuation, when completed, is to be taken for all purposes to be part of the valuation in force in respect of the relevant valuation district.

(3)  In making a supplementary valuation under subsection (1) , the Valuer-General must have regard to –

(a) the general level of valuations in the relevant valuation district, as existing at the date on which the last valuation under this Act of all lands within that valuation district came into force; and

(b) the value that the land to which the supplementary valuation relates would have had if, at that date, it had been in the condition in which it is at the time of the making of the supplementary valuation.

(4)  Until an order is made under section 20(11) in respect of a valuation district, a supplementary valuation of any land in that district is to be made in accordance with the Land Valuation Act 1971 .