The comparative factor is an official coefficient set each year for a municipality. It brings your municipal assessment to the market level of the current year. In Montreal, it is 1.00 in 2026, according to the City. This article gives the formula, explains why there is no factor by borough, and shows its effect on the welcome tax. The conceptual comparison between assessment and market value is covered in a dedicated article.
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1. The Official Formula
Estimated market value = Municipal assessment × Comparative factor
For a buyer, its most concrete official use is the calculation of transfer duties(welcome tax): the tax base is the highest of the price paid (excluding GST and QST), the consideration stated in the deed, and the municipal assessment multiplied by the comparative factor.
2. Montreal Triennial Roll: 2023-2025 vs 2026-2028
Quebec’s property assessment system operates on triennial rolls. The 2023-2025 roll covered fiscal years 2023, 2024 and 2025, based on market values as of July 1, 2021. The new 2026-2028 roll takes effect January 1, 2026 and is based on values as of July 1, 2024.
⚠️ Important: for 2026, the first year of the 2026-2028 roll, the City of Montreal sets the comparative factor at 1.00. A factor above 1 found elsewhere almost always refers to the previous roll.
3. One Factor for the Whole City
The comparative factor is set for the entire municipality, not by borough or by property category. Every property in Montreal, from the Plateau to Pointe-aux-Trembles, therefore uses the same factor of 1.00 in 2026. The “by borough” tables that circulate are not official values.
Each municipality has its own: Quebec City, whose roll is older, applies a factor of 1.08 in 2026, for example. Market differences between neighbourhoods of the same city show up in comparable sales, not in the factor.
4. Concrete Calculation Example
Case: single-family home in Montreal, assessed at $580,000 on the 2026-2028 roll
2026 adjusted value: 580,000 × 1.00 = $580,000
Purchase at $650,000: the price exceeds the adjusted value, so the welcome tax is calculated on $650,000, or $8,349.
Purchase at $540,000 (estate, quick sale): the adjusted value is higher, so the tax is calculated on $580,000, or $6,949 instead of $6,210.50.
The amounts apply the City of Montreal’s 2026 brackets, detailed in our article on the Montreal welcome tax in 2026. To estimate a property’s real value, the factor is not enough: compare it with recent sales on the same street or in the same building, which is what our estimator does.
5. Method Limitations
The comparative factor is an average coefficient that does not account for:
- Major renovations completed after the assessment date
- Overall condition, view, floor (for a condo), exposure
- Sub-borough variations (e.g.: Saint-Henri vs Pointe-Saint-Charles within Le Sud-Ouest)
- Market movement between the assessment date and today
For accurate estimation, cross the comparative factor with an analysis of recent comparables (last 12 months) on similar properties.
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