Gov. Code, § 56706

(a) Within 30 days, excluding Saturdays, Sundays, and holidays, after the date of receiving a petition, the executive officer shall cause the petition to be examined by, in the case of a registered voter petition, the county elections official, in accordance with Sections 9113 to 9115, inclusive, of the Elections Code, or in the case of a landowner petition, the county assessor, and shall prepare a certificate of sufficiency indicating whether the petition is signed by the requisite number of signers.

(b) (1) Except as provided in paragraph (2), if the certificate of the executive officer shows the petition to be insufficient, the executive officer shall immediately give notice by certified mail of the insufficiency to the proponents, if any. That mailed notice shall state in what amount the petition is insufficient. Within 15 days after the date of the notice of insufficiency, a supplemental petition bearing additional signatures may be filed with the executive officer.

(2) Notwithstanding paragraph (1), the proponents of the petition may, at their option, collect signatures for an additional 15 days immediately following the statutory period allowed for collecting signatures without waiting for notice of insufficiency. Any proponent choosing to exercise this option may not file a supplemental petition as provided in paragraph (1).

(c) Within 10 days after the date of filing a supplemental petition, the executive officer shall examine the supplemental petition and certify in writing the results of his or her examination.

(d) A certificate of sufficiency shall be signed by the executive officer and dated. That certificate shall also state the minimum signature requirements for a sufficient petition and show the results of the executive officer’s examination. The executive officer shall mail a copy of the certificate of sufficiency to the proponents, if any.