What Connecticut's statewide assessment data shows
Connecticut publishes every town's assessment roll in one place, at a flat 70% ratio with no equaliser. That makes it the easiest state in the country to check whether your assessment is fair.
Most states make comparing your assessment to your neighbours' unnecessarily hard. Data lives with 3,000-odd individual counties, in incompatible formats, behind portals designed for one lookup at a time.
Connecticut is the exception, and by some distance. All 169 towns publish to a single statewide dataset in a single schema. If you own property there, you have an advantage most Americans do not.
One ratio, no equaliser
Connecticut assesses at 70% of fair market value, statewide, under CGS 12-62a. There is no equalisation factor and no county-by-county variation.
The arithmetic on your own bill is therefore short:
| Step | Example |
|---|---|
| Assessed value on your notice | $280,000 |
| ÷ 0.70 = what the town thinks it is worth | $400,000 |
| × mill rate ÷ 1,000 (say 32 mills) | $8,960 a year |
Compare with Illinois, where a Cook County homeowner needs the 10% ratio, a 3.0355 equalisation factor, the exemption stack and a composite rate that varies by taxing district before the same question can be answered. Connecticut needs one division.
What the roll looks like
The statewide file carries what you would expect from a CAMA system: living area, assessed building and land split separately, appraised total, neighbourhood code, year built, grade, condition, land acreage and location. Two valuation years are published, 2024 and 2025.
The separate building and land assessment lines matter more than they look. A uniformity comparison must run on the improvement assessment divided by improvement area — building value against building size. Dividing a total that includes land by a floor area mixes two quantities and produces a figure that means nothing, while looking perfectly plausible.
What we found
Running the same peer comparison we run in Illinois — same town, same neighbourhood code, similar size and age — the median gap among Connecticut properties that clear our threshold is 21%.
The Illinois figure is 22%. Different ratio, different statute, different assessment cycle, different data pipeline; one percentage point apart. When two independent measurements of the same underlying thing agree that closely, it is reasonable to believe the thing is real.
Two traps in the data
Both cost us an import before we caught them, and both matter to anyone reading their own record.
Multi-building parcels. A parcel with several structures appears as several rows sharing one parcel key. The living areas must be summed and the assessment taken once. Counting the assessment per row multiplies a three-building property's value by three, and the property then looks catastrophically over-assessed when nothing is wrong.
Fields that hold impossible values. We found a year-built recorded as 18921989
— two years concatenated, presumably an original structure and an addition. A record like that will pass
straight through any pipeline that does not bound the value on the way in.
How to check your own
Divide your assessed value by 0.70. That is what the town believes your property would sell for. Would it? If it is meaningfully above what a realistic sale would fetch, that is your case, and it is the strongest kind: an over-valuation argument beats a uniformity argument in every jurisdiction.
Check the living area against your own measurement. Off by a few hundred square feet is common and directly moves the valuation.
Compare against your neighbourhood code, not the town. Towns contain very different areas. The code on your record card is the town's own grouping and is the right comparison set.
Note the valuation year. Connecticut revalues on a five-year cycle, so an assessment may reflect a market several years back. In a rising market that helps you; in a falling one it is the argument.
Sources
Connecticut statewide real estate sales and assessment data, valuation years 2025 (rny9-6ak2)
and 2024 (pqrn-qghw), published by the Office of Policy and Management. Mill rates by town are
published separately and change annually — always use your own town's current rate rather than an average.