A series LLC is a form of limited liability company that provides liability protection to multiple "series". Essentially, it's a master LLC with separate divisions, each protected and operating independently. As an entity, the series LLC is geared towards businesses where investors own multiple companies, with each series being protected from the debts and obligations of the other series. Currently, only several states support this option, including Delaware, Illinois, Iowa, Nevada, Oklahoma, Puerto Rico, Tennessee, Texas, and Utah.
On the other hand, if you are not responsible for its tax, then you should declare the equipment in Part III of the Business Property Statement (Equipment belonging to others). Where equipment is declared in Part III of the Business Property Statement, the Assessor will also send a Notice to File to the person reported as the equipment's actual owner.