Cal. Rev. & Tax. Code § 731

Each year between the first day of January and the first day of June, upon valuing the unitary property of an assessee, the board shall mail to the assessee, at its address as shown in the records of the board, a notice stating the amount of the assessed value of the assessee’s unitary property. The notice shall advise the assessee that a petition for reassessment of the unitary property may be filed, not later than July 20 of the year of the notice, at the headquarters of the board in Sacramento.