(a) If the change in ownership occurs or the new construction is completed on or after January 1 but on or before May 31, then there shall be two supplemental assessments placed on the supplemental roll. The first supplemental assessment shall be the difference between the new base year value and the taxable value on the current roll. In the case of a change in ownership of the full interest in the real property, the second supplemental assessment shall be the difference between the new base year value and the taxable value to be enrolled on the roll being prepared. If the change in ownership is of only a partial interest in the real property, the second supplemental assessment shall be the difference between the sum of the new base year value of the portion transferred plus the taxable value on the roll being prepared of the remainder of the property and the taxable value on the roll being prepared of the whole property. For new construction, the second supplemental assessment shall be the value change due to the new construction.

(b) If the change in ownership occurs or the new construction is completed on or after June 1 but before the succeeding January 1, then the supplemental assessment placed on the supplemental roll shall be the difference between the new base year value and the taxable value on the current roll.

(c) If there are multiple changes in ownership or multiple completions of new construction, or both, with respect to the same real property during the same assessment year, then there shall be a net supplemental assessment placed on the supplemental roll, in addition to the assessment pursuant to subdivision (a) or (b). The net supplemental assessment shall be the most recent new base year value less the sum of (1) the previous entry or entries placed on the supplemental roll computed pursuant to subdivision (a) or (b), and (2) the corresponding taxable value on the current roll or the taxable value to be entered on the roll being prepared, or both, depending on the date or dates the change of ownership occurs or new construction is completed as specified in subdivisions (a) and (b).

(d) No supplemental assessment authorized by this section shall be valid, or have any force or effect, unless it is placed on the supplemental roll on or before the applicable date specified in paragraph (1), (2), (3), or (4), as follows:

(1) The fourth July 1 following the July 1 of the assessment year in which the event giving rise to the supplemental assessment occurred.

(2) The eighth July 1 following the July 1 of the assessment year in which the event giving rise to the supplemental assessment occurred, if the penalty provided for in Section 504 is added to the assessment.

(3) The eighth July 1 following the July 1 of the assessment year in which the event giving rise to the supplemental assessment occurred, if the change in ownership was unrecorded and a change in ownership statement required by Section 480 or preliminary change in ownership report, as required by Section 480.3, was not timely filed.

(4) Notwithstanding any other law, in the case where property that is owned by a community land trust and was previously exempt pursuant to Section 214.18 becomes subject to taxation pursuant to subdivision (d) of that section, any assessment made in the amount of an exemption, or that portion of the exemption, previously allowed pursuant to Section 214.18 shall be made within five years of the lien date following the date on which the property becomes subject to taxation.

(5) Notwithstanding paragraphs (1), (2), (3), and (4), there shall be no limitation period on making a supplemental assessment, if the penalty provided for in Section 503 is added to the assessment.

For the purposes of this subdivision, “assessment year” means the period beginning annually as of 12:01 a.m. on the first day of January and ending immediately prior to the succeeding first day of January.

(e) If, before the expiration of the applicable period specified in subdivision (d) for making a supplemental assessment, the taxpayer and the assessor agree in writing to extend the period for making a supplemental assessment, correction, or claim for refund, a supplemental assessment may be made at any time prior to the expiration of that extended period. The extended period may be further extended by successive written agreements entered into prior to the expiration of the most recent extension.

(Amended by Stats. 2019, Ch. 669, Sec. 2. (SB 196) Effective January 1, 2020.)