Amended and supplementary notices: what they change

Four possible notices

Most owners get one notice a year. Calgary points out that others can follow. The table sums up where each comes from. In the part of the Act on review boards, “assessment notice” “includes an amended assessment notice and a supplementary assessment notice” (MGA, s. 453(1)(a)), so the complaint rules apply to each one.

The amended assessment notice

An amended notice follows a correction. If an error, omission or misdescription is found on the roll, the assessor may correct it for the current year only, and an amended notice must be sent (MGA, s. 305(1)). Either side can find the error: Edmonton writes “If the City or a property owner discovers an error.” The Act also calls for an amended notice when exempt property becomes taxable, or the reverse (s. 305(3)).

Calgary says the amended notice replaces the previous annual notice. It must be sent no later than the date tax notices must be sent (s. 310(1.1)). The assessor sets a separate notice of assessment date for it, which cannot be later than that same date (s. 308.1(2)).

An amended notice can also arrive during a complaint. If the assessor corrects an assessment under complaint, a copy goes to the board no later than one day after it is sent to the owner (MRAC, s. 14). If that copy arrives before the hearing, the complaint is cancelled, the fee is refunded and you have a new right of complaint on the amended notice (MGA, s. 305(1.2)). Read it carefully: the new value may or may not satisfy you.

The supplementary assessment notice

The annual notice reflects the property as of December 31. A house finished in May is not on it. To tax the house in the year it is built, the municipality must pass a supplementary assessment bylaw. That bylaw applies to the year only if it is passed “before May 1 of that year” (MGA, s. 313(3)). Calgary and Edmonton both issue supplementary notices.

The assessor then prepares a supplementary assessment for an improvement completed during the year, occupied during the year or moved into the municipality (s. 314(2)). It reflects the value of an improvement never assessed before, or the increase in value since it was last assessed (s. 314(3)). It is prorated by month, counting the whole of the first month (s. 314(4)). The supplementary roll and notices must be done before the end of the year (ss. 315 and 316).

Edmonton describes the typical case. If the home was only partly complete on December 31, the annual notice reflects the land plus the building “based on its completion percentage.” If the building was added after that date, the record shows vacant land. The supplementary notice then shows the increase from the new construction and the number of supplementary months, meaning the months the property was completed or occupied.

The effect on your tax

A council that authorizes supplementary assessments must, in the same year, pass a supplementary tax bylaw, and it “must use the tax rates set by its property tax bylaw” (MGA, s. 369(2)). There is no special rate for new homes.

Calgary publishes its calculation: supplementary assessed value × the applicable tax rate, divided by 12, multiplied by the supplementary months. The bill is sent separately from the notice. If the number of supplementary months is 3, the bill covers October, November and December. For a Tax Instalment Payment Plan (TIPP) participant, the monthly instalment is recalculated. Edmonton says the supplementary tax notice shows the additional amount due by the date on the notice.

Fictional example, to redo with your own numbers: a supplementary value of $300,000, a fictional rate of 0.0100 and 3 supplementary months. The supplementary tax is $300,000 × 0.0100 ÷ 12 × 3 = $750. Use the rate on your tax notice. The general method is explained in cost and savings.

How long you have to appeal

The deadline is still “60 days after the notice of assessment date” (MGA, s. 284(4)). The Act requires the assessor to set additional notice of assessment dates for amended and supplementary notices (s. 308.1(2)). Each notice therefore carries its own deadline, which the law requires to be printed (ss. 309 and 316.1). The annual deadline, March 23, 2026 in Calgary and Edmonton, does not apply.

Edmonton says owners have “60 days from the time of the mailing” to review an amended notice. Calgary says its review period “applies to supplementary assessment notices as well” and that the dates are on each notice. Read the printed date: that is the one that counts.

The complaint follows the general rules: prescribed form, the fee set by council (MGA, s. 460(2)), a requested value and every issue checked. The decision runs on a different clock: for a supplementary or amended notice, a LARB decides within 160 days of filing and a CARB within 210 days, or before the end of the taxation year if that is later (MRAC, s. 57). The risk of an increase applies here too (MGA, s. 467(1.1)).

What to check on a supplementary notice

• The number of months. It depends on when the home was completed or occupied, with the first month counted in full.
• The date used. Calgary prints the date the supplementary assessment is based on. A transfer document, an occupancy permit or a final invoice may contradict it.
• The added value. It covers construction not yet assessed, or the increase since the last assessment (s. 314(3)). Compare it with sales of similar new homes. See evidence that works.
• The property details. Area, basement, garage: the checklist is in errors in your property record.

Frequently asked questions