General Information. However, Stock sales are not subject to sales taxes.Asset Sale Planning. Browse 127 businesses for sale in Contra Costa County, CA on BizBuySell. You will need to allocate the amount reflected on form 8594 among all the assets. A typical method is to allocate the proceeds based on the original cost. A gain results when an asset is disposed of in exchange for something of greater value. The most Contra Costa County, California businesses for sale listings including franchises, opportunities and businesses. Contra Costa County - Business License Online Application ; Select your business type ; Will your business operate inside the unincorporated areas of the county?