http://ottawa.ca/en/city-hall/budget-and-taxes/property-taxes/supplementary-assessment
What is a supplementary assessment?
A supplementary assessment is an additional assessment (increase in value) resulting from property improvements or changes, which were not reflected in the property tax bill for the current year and occurred after the return of the assessment roll. A supplementary assessment can be processed for the following reasons:
- There is an increase in property value because of a new building or improvement
- A property ceases to be exempt from taxation or ceases to be eligible for assessment at the farm, managed forest, or conservation land classes
- A property ceases to be classified in a subclass of real property, farmlands awaiting development, commercial or industrial vacant land
- A property becomes liable for taxation in a different property class
What is an omitted assessment?
An omitted assessment is an additional assessment resulting from building a new structure (i.e. home) or addition, which was not previously recorded on the annual assessment roll. An omitted assessment can be processed for the current tax year and two preceding tax years for the following reasons:
- There is an increase in property value because of a new building or improvement
- To assess and classify land that was previously exempt
- A property ceases to be classified as managed forest or conservation land
How does the supplementary/omitted assessment work?
When the City issues a building permit, there will most likely be a value change in the property, which creates a supplementary/omitted assessment. Your property assessment will need to be updated to reflect the completed work as a result of the building permit. The Municipal Property Assessment Corporation (MPAC) will mail you a supplementary or omitted assessment notice that outlines such assessment values and the effective date(s) they take effect.
What is a supplementary/omitted tax bill?
For taxation purposes, you will receive a tax bill at a later date called a "supplementary" tax bill. The supplementary tax bill will reflect the additional change in your assessment and taxes owing will be adjusted accordingly.
If the supplementary/omitted tax bill is for a new home, you, as the owner, will be responsible from the effective date of occupancy and/or possession; therefore, creating multiple year supplementary/omitted tax bills.