Weblearn what supplemental tax bills are, when and why they are issued, how they are calculated, and how to pay them. Find out how to dispute a bill if you think it is. Weblearn about supplemental assessment, a type of property tax bill issued when the assessed value changes due to ownership or new construction. Find out how to get a notice, pay, appeal, and apply for exemption. When the assessor's office reappraises your property due to a change in ownership or completion of new construction, you will be notified by mail of.