Official Forms for Viewing and Downloading. Access forms available from the Assessor's office, including benefits, business personal property, change in ownership, and other general forms.Total of 103 forms are available for Contra Costa County for 2023. FSBO transactions in California can be complicated. Here's everything a DIY seller needs to know in the Golden State. California requires those selling FSBO to fill out and file many documents and forms. Several of these documents are legally binding agreements. Forget about Agent Commissions! The below link will take you directly to the Assessor's Office forms page. The PCOR is near the bottom of the page under "Change in Ownership Forms".