Cook County's triennial reassessment and the three triads
Your township is reassessed every third year. Knowing which year is yours changes when to act.
Cook County reassesses every property once every three years, and the county is divided into three groups — the triads — so one third is reassessed each year.
The three triads
| Triad | Covers |
|---|---|
| City | The eight townships within Chicago — Hyde Park, Jefferson, Lake, Lake View, North Chicago, Rogers Park, South Chicago, West Chicago |
| North | The northern suburban townships — Evanston, New Trier, Niles, Northfield, Maine, Wheeling, Barrington, Elk Grove, Hanover, Palatine, Schaumburg, Norwood Park, Leyden |
| South | The southern and western suburban townships — Berwyn, Bloom, Bremen, Calumet, Cicero, Lemont, Lyons, Oak Park, Orland, Palos, Proviso, Rich, River Forest, Riverside, Stickney, Thornton, Worth |
What happens in your reassessment year
Your value is rebuilt from scratch. The model is re-run against recent sales and your property receives a new value reflecting what the market has done since the last cycle.
In a rising market this is where the large increases appear — three years of movement arriving in one notice. A 30% increase sounds outrageous; spread over the three years it represents, it may be an ordinary market.
What happens in the other two years
Your assessed value normally carries forward unchanged, except for new construction or demolition, a change of use, a correction, or a change in the state multiplier — which can move your equalised value with your assessed value untouched.
The cycle changes what argument is available
In your reassessment year, the value is fresh and the sales behind it are recent. A market-value argument has to contend with data the office has just examined. But this is also when the most new errors enter the roll, because every parcel was re-valued at once — so the record is worth checking closely.
In an off year, your value reflects a market that may have moved. If values fell since the reassessment, your assessment describes a market that no longer exists. Illinois allows an appeal in every year, not only reassessment years, and this is the situation people most often fail to notice — because nothing on the notice changed.
Why winning early in a cycle is worth more
A reduction generally holds until the next reassessment. Win in the first year of your triad's cycle and it runs for three years; win in the third and it is reset almost immediately.
Finding your year
The Assessor publishes the triad schedule and the township-by-township calendar. Two dates matter: when your township is reassessed, and when your appeal window opens and closes. They are not the same, and the second is the one that ends things.