A successful challenge generally rests on one of two arguments: the City's record of your property contains a factual error, such as the wrong square footage or a garage that no longer exists, or your assessment is out of step with what genuinely comparable properties in your area sold for.
What does not work as a challenge is arguing that the tax bill itself is too high in absolute terms, or comparing your mill rate to another municipality's, since neither of those speaks to whether your specific assessed value, taxed at 80 percent, is accurate.
Before filing, pulling your own property record from the city and checking it against actual recent sales tells you whether you have a real case. Get your hand-reviewed valuation from Joel Dyck.