General Information. Access forms available from the Assessor's office, including benefits, business personal property, change in ownership, and other general forms.Both the seller and purchaser of a group of assets that makes up a trade or business must use Form 8594 to report such a sale. Total of 103 forms are available for Contra Costa County for 2024. Please Download PDF BOE-571-S REV. Contact Us. Registrar of Voters. 925-335-7800. Exemption forms are due June 30th each year. Once forms are filed exemption is automatically renewed each year. Declaration Form (FL-150) if you are requesting financial orders from the court.