The City of Saskatoon assesses residential property at 80 percent of market value, and if a homeowner believes that assessment is inaccurate, they can file an appeal to the Board of Revision within the window the City sets after assessment notices go out. Selling is not a condition of that process.
A sale can be a reason someone notices a discrepancy, since a hand-reviewed valuation sometimes surfaces a gap between assessed value and actual condition, but the appeal itself is a separate City process open to any owner, tied to the assessment notice, not a listing.
If you are unsure whether your assessment reflects your home's actual condition, that is worth checking either way. Get your hand-reviewed valuation from Joel Dyck.