The Car Tax Change

The oldest vehicles: a $500 floor

The statute sets a minimum assessment of $500. In Colchester's bills, vehicles of model year 2005 and newer are assessed at a percentage of MSRP; model year 2004 and older are assessed at exactly $500, and one more model year crosses that line each year. For a 20-year-old vehicle that still carried real book value, this was a large cut — a 2004 pickup in the sample went from a $257 bill to a $15 bill. For the many older vehicles already assessed at or near $500 under the old method, the assessment did not move at all, so their bill rose by the full mill rate increase. That is why the 20-plus-year group shows the highest share of rising bills and the lowest share of rising assessments in the same chart above.

Did the change itself raise taxes, or just move them around?

This is the question residents most want answered, and it is the one this data answers least well. Two things changed between the two bills besides the law: every vehicle got a year older, and used-car prices kept cooling from their pandemic peak. Separating the law from those requires estimating what the old book-value method would have produced on October 1, 2024 — a number nobody recorded.

Estimating it from Colchester's own bills — using how much assessments actually fell under the old method between the 2022 and 2023 grand lists, adjusted for the difference in used-vehicle price drift between the two years — changes the median vehicle's assessment by — relative to what the old method would have given, across every used-vehicle price drift assumption tested. In other words, close to a wash for the typical vehicle. The size of that estimate is withheld pending the correction described below.

The per-vehicle split from that estimate is not reliable, and is not reported here. Running the identical calculation across a pair of years when the law did not change produces a near-even up-and-down split anyway — — — because applying one average depreciation rate to every vehicle turns each vehicle's ordinary variation into an apparent effect. The median survives that test; a headcount does not.

Correction pending on these two figures. The depreciation-rate estimator behind the range and the placebo above is fitted on passenger vehicles only, but the version that produced these numbers applied it to every vehicle class, including trailers, for which no rate was fitted. The fault is in the analysis script, which has been corrected in the project repository (CarTaxAnalysis/viewb2.py); restating the two figures needs the original bill capture, which is not published because it carries owner names, so they are left as computed and flagged here rather than quietly replaced. Re-running the corrected script on a reconstruction of the sample moves the range by a few points and leaves the placebo a near-even split, so the conclusion these figures support — that the median is reportable and a per-vehicle headcount is not — does not depend on the correction. Nothing else on this page uses that estimator: the headline splits, the make-by-make pattern and the schedule derivation are all measured directly from the bills.

What can be said plainly: the town's total motor vehicle grand list fell 6.4%, most of the decrease residents saw in their own bills came from vehicle age and a cooling used-car market rather than from the law, and the law's clearest effect was on who pays — the make-by-make pattern above, which needs no counterfactual at all.

Where does your own vehicle sit?

Both figures are on your own bills, and both are public at Colchester's tax bill lookup — search your name and read the total tax on the two motor vehicle bills for the same vehicle.

This compares your two bills. It does not separate the valuation change from the mill rate change or from your vehicle getting a year older.

What Colchester chose, and what it changed

The 2024 law gave every town the same schedule. A February 2025 emergency act (Public Act 25-2) then offered towns an optional schedule five percentage points higher at every step, and let them re-publish a grand list already filed.

Colchester's Board of Selectmen took the option on March 6, 2025, voting 4-0 to "enact the local option … and enable the town assessor to republish the October 1, 2024, motor vehicle Grand List utilizing the optional depreciation schedule." The assessor's figures put the regular motor vehicle list at $149.9 million under the default schedule against $165.6 million under the option, with a further $1.6 million on the supplemental list — a combined $17.3 million of assessment, which the assessor's handout valued at roughly $496,000 of tax at the prior year's mill rate. The list as finally certified came in at $164.4 million, slightly below the estimate.

Every vehicle assessment on this page therefore reflects the higher, optional schedule. Applying the default schedule to the same sampled vehicles, — of bills would have fallen rather than —, with a median change of — instead of —.

Colchester's schedule, October 1, 2024 grand list

The step between model years was read out of the bills themselves, by comparing the same vehicle's assessment on the 2024 and 2025 grand lists — a ratio that depends only on the schedule, since original sticker price does not change. Every model year steps down by exactly five points, matching the optional schedule's ladder. The level — 90% in the first year rather than the default 85% — comes from the Board of Selectmen's vote, and the original sticker prices implied by the bills are consistent with it.

Assessment = MSRP × the percentage above × 70%. One detail of Colchester's practice differs from a literal reading of the statute: the statute's 20% band covers five years, but Colchester applies 20% across six model years, 2010 through 2005, and the $500 minimum only from model year 2004. The MSRP comes to the assessor from the state DMV, keyed to the vehicle identification number, and is a base price that excludes destination charge and options; under the new law an appeal can challenge the MSRP used, but not the mileage or condition of the vehicle.

Detail by model year

Rows are unweighted counts within the sample as drawn, not estimates of town-wide shares. Model-year rows rest on 5 to 33 vehicles each and are noisy; the age bands in the chart above are the more reliable cut. Model years 2004 and older are omitted here because they sit at the $500 floor rather than on the percentage schedule.

Methodology

Where the numbers come from

Connecticut publishes no per-vehicle assessment data, and neither the state, the Office of Policy and Management, the Connecticut Conference of Municipalities, nor any town has published a count of vehicles whose assessments rose or fell. Colchester's own motor vehicle grand list is not published either. What is public is every individual tax bill, through the town's bill lookup.

On August 21, 2026, 250 motor vehicle grand list numbers were drawn at random from the October 1, 2024 list, whose highest list number in use is about 10,879. Each drawn account was then looked up by name to recover the same vehicle's bills on the adjacent grand lists. That produced 1,184 distinct owner-and-vehicle records, of which 519 carried a taxable bill on both the 2023 and 2024 lists — the paired set used throughout. The population is motor vehicle bills, which includes vehicles registered to businesses as well as to households; two commercial fleets appear in the sample and are down-weighted accordingly.

From tax to assessment

The lookup shows the tax charged, not the assessment. Colchester applies a single mill rate to all property with no overlapping district rates, so assessment = tax ÷ mill rate × 1,000. Mill rates come from OPM's published series: 28.67 for the October 1, 2023 list and 29.92 for the October 1, 2024 list. As a check, 97.7% of derived assessments come out as whole multiples of $10, as assessments are recorded — a result that would not hold if the mill rate or the arithmetic were wrong. Records failing that check are dropped; they appear to be bills adjusted mid-year, though the check is a partial screen rather than a complete one, since a bill prorated to exactly half still lands on a $10 boundary. A handful of such half-value bills remain in the sample.

How the percentages are estimated

Because the name lookup returns every household sharing a surname and first initial, larger name groups are more likely to be drawn. The headline percentages therefore weight each vehicle by the inverse of its name group's size, which is the standard correction for that kind of sampling; confidence intervals come from 4,000 bootstrap resamples over name groups. As a check, the vehicles that were themselves the random draw — a plain random sample needing no weighting — give a share of rising bills within about one point of the weighted estimate. The breakdowns by age, make and model year are not weighted. They describe the sample as drawn, in which larger name groups are over-represented, so they serve to compare groups with one another and are not estimates of town-wide shares; the headline figures above are the only population estimates on this page.

What this cannot tell you

• It is a sample, not a census. The headline share of bills that rose carries a 95% confidence interval of roughly —. An exact count would require the assessor's grand list files.
• The unit is a vehicle, not a household. A two-car household appears twice, and a household whose cars moved in opposite directions is not counted as either.
• Newly exempt trailers are held out of the headline. A separate 2024 law exempted personal-use utility trailers, snowmobiles and all-terrain vehicles. — Including them, the share of bills rising falls to — and the share falling rises to —, with a median change of —. They are excluded from the headline because their bills went to zero for a reason unrelated to the valuation schedule.
• Vehicles that appear on only one list are excluded. There is no prior bill to compare, so a resident who replaced a car will not see their situation here. Because the sample is drawn from the 2024 list, households that left Colchester entirely between the two years cannot enter it at all, so the count of departures is a lower bound.
• Supplemental bills are excluded. Vehicles registered part-way through a year are billed separately and prorated, which is not comparable year to year.
• Matching is by owner name and vehicle description, not by VIN. A household with two identical vehicles cannot be told apart; about 3% of records are affected, and alternative tie-breaking rules move the headline split by less than a quarter of a point.
• A second 2024 change touched the same bills. A disabled-veteran exemption was expanded. It is not part of the valuation change and is not separated out here.