The property tax amount is used to help calculate the Ontario Trillium Benefit.
The Ontario trillium benefit (OTB) is the combined payment of the Ontario energy and property tax credit, the Northern Ontario energy credit, and the Ontario sales tax credit. The annual OTB entitlement is usually divided by 12 and the payments issued monthly. Your 2017 OTB payments, which are based on your 2016 income tax and benefit return, will be issued on the 10th of each month, starting on July 10, 2017
http://www.cra-arc.gc.ca/E/pbg/tf/5006-tg/5006-tg-16e.pdf