Michigan law prohibits assessors from assessing properties at 50% of a sale price. Whether or not a property has sold, the assessor must value properties using sales from a state-required time period and the same mass appraisal methods used to value properties that have not sold.
Although you receive your assessment change notice in early March each year, your value estimate does not reflect "current" market value. Using a 2-year study, we are required to use sales that occurred between October 1, 2012 - September 30, 2014 for the 2015 value estimates. You should use this same time period when comparing sales to your new property value estimate.