The Board of Revision looks at whether the assessed value reflects market value as of the City's valuation date, not at whether your tax bill feels high, so the strongest appeals come with sale prices of genuinely comparable homes, backed by a home inspection running $400 to $600, rather than a general complaint about cost.
An agent's comparable-sale evidence is different from what an online estimate produces, because it accounts for condition and permit status the way a buyer actually would, which is often the gap between an assessment that looks too high and one that turns out to be accurate.
Building that evidence before the appeal deadline, not after, is what actually moves a Board of Revision decision. Get your hand-reviewed valuation from Joel Dyck.