Using a house price index to adjust a value between dates
A price index lets you move a value from one date to another: value × (index at the new date ÷ index at the old date). It's how you bring a comparable sale to your assessment's valuation date, or put an old assessment in today's terms. Use an index for your own area and home type, and remember an index tracks typical homes, not yours.
The formula
Adjusted value = value × (index at the target date ÷ index at the original date). A sale of $700,000 when the index was 140, adjusted to a valuation date when it was 125, becomes $625,000.
Three practical uses
- Assessment appeals: bring recent comparable sales back to the valuation date (BC: July 1 last year; Montréal: July 1, 2024).
- Understanding an old assessment: roughly translate an Ontario 2016-date assessment to today.
- Tracking equity: estimate how far your value may have moved since your last appraisal, to test in the equity calculator.
Which index
Common Canadian options include Statistics Canada's New Housing Price Index (new homes only), and resale indexes published by industry bodies and data providers. Use the one your assessor or appraiser would recognize, and note its date and source with your figures.
Limits
Indexes lag, smooth out local swings and don't know your renovations. OSFI flags rapidly rising markets as higher-risk for valuations; in fast markets, recent sales beat any index.
Frequently asked questions
Can I use an index to estimate my home's value?
Only roughly: it tells you how typical homes moved, not how yours did. For borrowing, the lender's appraisal decides.
Primary sources
- OSFI — Guideline B-20: Residential mortgage underwriting (HELOC 65%, appraisals, AVMs) (effective October 31, 2017). Checked .
- Appraisal Institute of Canada — What appraisers do (AACI, CRA designations; three approaches). Checked .