§ 1803. Base proportions and adjusted proportions; determinations. 1.
Base proportion. The legislative body of each special assessing unit
shall establish the base proportion for each class and a base proportion
for each class for each portion and each town and county special
district and zone of assessment included within its boundaries.

2. Adjusted proportions. (a) For assessment rolls prepared during and
after nineteen hundred eighty-two and before nineteen hundred
ninety-one, and for assessment rolls prepared after two thousand one for
purposes of all county and town special districts and zones of
assessment, the legislative body of each special assessing unit shall
adjust such base proportions to reflect the addition to the assessment
roll of new property, additions to or improvements of existing property
or formerly exempt property or the full or partial removal from the roll
of property by reason of fire, demolition, destruction or new exemption
or any change in the class designation of any parcel of real property;
provided, however, that the legislative body of each special assessing
unit may further alter the base proportions, as so adjusted, in
accordance with the provisions of paragraph (b) of this subdivision.

(b) Any further such alterations for any class in any year may not
exceed five percent of the base proportions or adjusted proportions used
for the immediately preceding tax levy, provided that in each year the
sum of any such proportions for such special assessing unit or portion
thereof, or town or county special district or zone of assessment
included therein, shall equal one. Such alterations may vary among
portions and among town and county special districts; provided, however,
that for town and county special districts and zones of assessment, any
such alterations shall not be inconsistent with any changes in the value
of the class in the special district as indicated by the assessed value
of the class in the special district and the most relevant class
equalization rates certified by the commissioner pursuant to section
twelve hundred twelve of this chapter.

3. Town and county special districts. For purposes of town and county
special districts that are not portions, the base proportion shall be
determined by using the final assessment roll filed in calendar year two
thousand one. The base proportion of a zone of assessment established
from the territory of a prior district, as such term is defined in
paragraph (f) of subdivision one of section four of chapter six hundred
eighty-five of the laws of two thousand three, shall be determined by
using the base proportion of the prior district with such adjustments,
if any as are required by paragraph a of subdivision two of this
section.