253.3. To establish the percentage of increase of the taxable value of a unit of assessment, its taxable value entered on the roll for the fiscal period considered, as it exists on the date of preparation of the account for real estate taxes under section 81, is compared to its taxable value entered on the roll for the preceding fiscal period, as it existed at the end of that period, taking into account the alterations made to the roll before the preparation of the account.
For the purposes of the first paragraph, the value of all or part of an immovable added to the unit by an alteration to the roll pursuant to paragraph 7 of section 174 for the fiscal period considered is not taken into account, unless the alteration also affects the roll for the preceding fiscal period.
The first two paragraphs apply subject to the second paragraph of section 253.5.