A supplementary tax bill is issued by the City and reflects any additions or improvements
you have made to your property.
You receive a supplementary tax bill for one of the following reasons:
- you had some renovations/improvements done to your property that has increased its current
- you have constructed a building on the property
- there has been a change in the use of your property resulting in a change in the tax class
of your property assessment.
There are two methods of calculating your supplementary taxes:
- First year supplementary: The first year, for which a supplementary
or omitted assessment is issued, the supplementary taxes are calculated by multiplying the tax
rate by the supplementary assessment and applying the most recent level of
taxation. The result is then prorated for the number of days from the effective
- Subsequent year supplementary: To calculate supplementary taxes for
a second or subsequent tax year for a single event, the tax level for the property is
recalculated inclusive of the supplementary or omitted assessment. The supplementary
taxes are then calculated by multiplying the tax rate by the supplementary assessment and
applying the revised tax level up to a maximum of 100%.
Supplementary taxes for properties with assessment in more than one capped class are
calculated independently by class.
Residential and Farmland Awaiting Development Assessment: Supplementary taxes are
calculated by multiplying the tax rate by the supplementary assessment and prorating for the
number of days from the effective date.
As a result of a supplementary tax billing, the tax level of a property could be revised for
the year of a supplementary and or any subsequent year(s). Previously billed taxes are
recalculated to reflect the revised tax level.
For adjustments to previously billed taxes, see Capping Recalculation, Charge or
Credit on your supplementary bill.
Your supplementary taxes are due in three instalments. If you are currently enrolled
in the preauthorized tax program, your supplementary taxes will be withdrawn from your bank
account on your next withdrawal dates. If you wish to enrol in the preauthorized tax
program, please call the Customer Service Centre at 3-1-1, or if calling outside the
City limits call 905-615-4311 or e-mail at firstname.lastname@example.org.
The Municipal Property Assessment Corporation (MPAC) is responsible for the valuation
function of all properties in Ontario.
Under the Assessment Act, MPAC can provide the municipality with assessment values where the
assessment has been omitted from the current assessment roll and/or the assessment rolls of
either of the two preceding years or when there is an increase in assessment for the current
year, for such things as new buildings or additions/improvements.
From the information supplied by MPAC, the City of Mississauga calculates the tax amounts
due and issues tax bills. Until the City receives the information from MPAC, a
supplementary tax bill cannot be issued. Consequently there may be a considerable time
lapse from the effective date of the supplementary until you receive a tax bill.
If you think your supplementary assessment is incorrect, a reconsideration process is
available through MPAC, for which there is no fee. Visit the MPAC website at the related link
above for details on how to request a reconsideration.
You also have the right to appeal to the Assessment Review Board (ARB)which is an
independent tribunal. An appeal must be filed within 90 days of the date of the notice of
assessment. Visit the ARB website at www.arb.gov.on.ca for all the details on how to file an
For further information, please call the Customer Service Centre at 3-1-1, or if
calling outside the City limits call 905-615-4311 or e-mail at email@example.com.