Cal. Rev. & Tax. Code § 430.5
No land shall be valued pursuant to this article unless an enforceable restriction meeting the requirements of Section 422 is signed, accepted, and recorded on or before the lien date for the fiscal year to which the valuation would apply. To provide counties and cities with time to meet the requirement of this section, the land that is to be subject to a contract shall have been included in a proposal to establish an agricultural preserve submitted to the planning commission or planning department, or the matter of accepting an open-space easement or scenic restriction shall have been referred to that commission or department on or before October 15 preceding the lien date to which the contract, easement or restriction is to apply.
Ca. Rev. and Tax. Code § 430.5