An omitted assessment occurs when taxable property was not included in the assessment roll for a particular year, whether due to administrative error, incomplete records, or failure to identify property. When discovered, assessors add the omitted property to the roll, resulting in supplementary tax bills for years the property should have been assessed. Provincial legislation typically limits how far back omitted assessments can reach. Property owners may dispute omitted assessments if they believe errors exist. Omitted assessments ensure all taxable properties contribute fairly to municipal services, but retroactive bills can create financial hardship requiring payment arrangements or appeals.