This is the site that provides all info regarding Property Assessment.
To apply for a Request for Reconsideration go to the MPAC site for the form. Here is the appeal process.
Apparently the process changes a lot since I filed one in 2013 as the links I have doesn't. The links above are just searched online and you might have already got them.
What I did though, was sending an email ( the email is available from old links available at that moment. ) to MPAC. Something likes below:
The Assessed value of my property is $398,000. However, a similar property nearby located at 111 ABC Ave. was sold in June 2012 at $349,900. This property has the same builder, same style, same lot size and same size as ours. Considering current housing market, a value of our property of $350,000 or lower would be acceptable. Please kindly re-assess our property and we would be happy to provide any information you need.