18.4. Unless the owner has notified disagreement in accordance with section 18.3, only the information communicated by the assessor pursuant to section 18.2 shall be used for the purpose of determining the value of the structures that are part of an immovable in respect of which the method of assessment prescribed by a regulation under paragraph 10 of section 262 is mandatory.
Where the owner has notified disagreement in accordance with section 18.3, the following rules apply for the purpose of determining the value of the structures:
(1) the assessor cannot determine a cost new greater than the cost new that was communicated or subtract an amount less than the amount specified in the breakdown communicated under section 18.2;
(2) the owner cannot have acknowledged a cost new that is less than the cost new communicated or an amount greater than the amount specified in the breakdown.
The first and second paragraphs do not apply where, after the communication required under section 18.2 and referred to in the first paragraph, an event referred to in the second paragraph of section 46 occurs.