In Illinois, you need a recorded subdivision plat whenever you divide land into two or more parcels and any of the resulting parcels is smaller than five acres. The Illinois Plat Act (765 ILCS 205) sets that baseline, and local municipal or county ordinances add their own standards on top. The plat has to be prepared by an Illinois Registered Land Surveyor, approved by the right governing body, and recorded with the county recorder before you can legally sell lots or, in many places, pull building permits. These are the Illinois subdivision plat requirements that actually control whether your project moves forward or stalls at the recorder’s desk.
When a Subdivision Plat Is Required
The Plat Act is triggered by two conditions together: you are dividing a tract into two or more parts, and at least one of those parts is under five acres.1Illinois General Assembly. Illinois Code 765 ILCS 205/1 If both conditions are met, you need a plat.
Several situations fall outside that trigger. Divisions into parcels of five acres or more are exempt as long as no new streets or access easements are being created. There is also a one-time exemption that allows a single lot of under five acres to be split off from a larger tract, provided a licensed surveyor prepares a survey; the exemption disappears the moment you try to split off a second lot from the same original tract.2Illinois General Assembly. Illinois Code 765 ILCS 205/1 – Full Text
The access-road caveat trips up a lot of rural landowners. A five-acre split that looks exempt on paper may require a plat if you are cutting in a new driveway easement or private road to reach the back parcel. Check that detail before assuming you are clear.
What the Plat Must Show
The surveyor’s plat has to lay out the subdivision in enough detail that anyone reading it can locate every lot and improvement. Required elements include all proposed streets, alleys, utility easements, parks, school grounds, lots, and blocks, each with precise dimensions. The plat must also include topographic studies showing the elevation of the land before any grading begins.1Illinois General Assembly. Illinois Code 765 ILCS 205/1
The owner must acknowledge the plat in the same manner as a deed, and the surveyor must attach a signed statement. A notarized statement identifying the school district in which each lot or block lies also has to be included.
Who Approves the Plat
Which body approves your plat depends entirely on where the land sits.1Illinois General Assembly. Illinois Code 765 ILCS 205/1
- Land inside a city, village, or town’s corporate limits goes to the city council or village board of trustees.
- Land in contiguous territory covered by a municipality’s official plan also goes to that municipality.
- Land outside any municipal boundary or official plan area goes to the county board.
If your parcel straddles a boundary, or sits in an unincorporated area that a nearby municipality has placed within its official planning territory, call both offices before you file. Submitting to the wrong body wastes weeks.
Preliminary and Final Approval
Most municipalities and counties split review into two stages. Preliminary approval requires drawings showing proposed street locations and widths, sewer and storm drain placements, proposed dedications of public land, lot sizes, utility easements, and the planned method of sewage disposal. This stage exists so the municipality and the developer can identify problems before expensive final engineering begins. Final approval requires complete drawings and specifications, and often a performance bond guaranteeing the developer will finish required improvements such as streets, sewers, and sidewalks.3Illinois General Assembly. Illinois Code 65 ILCS 5/11-12-8
The improvement standards themselves come from local ordinances adopted under the Illinois Municipal Code, which lets municipalities regulate street width, surfacing, and layout; sidewalks and street lighting; residential lot sizes; storm drainage; water supply; and sanitary sewer systems.4Illinois General Assembly. Illinois Code 65 ILCS 5/11-12-5 These standards vary widely. A suburban village may require paved streets, curbs, and sewer connections; a rural county may accept gravel roads and septic systems. Pull the local subdivision ordinance before you design anything.
School, Park, and Impact Dedications
When a proposed subdivision will generate enough residents to warrant new school or park facilities, Illinois law allows the approving municipality to require the developer to dedicate land for those purposes before the plat is approved.3Illinois General Assembly. Illinois Code 65 ILCS 5/11-12-8 Many municipalities use formulas tied to the number of lots or projected student population, and most allow a cash contribution in place of a land dedication when outright dedication is not practical.
Factor these obligations in during early planning. A requirement that surfaces at the final approval stage can reshape the economics of the project.
There is also a constitutional limit on how far these demands can go. Under Nollan v. California Coastal Commission and Dolan v. City of Tigard, conditions on a land-use permit must have an essential nexus to a legitimate government interest and be roughly proportional to the development’s impact. The U.S. Supreme Court confirmed in Sheetz v. County of El Dorado (2024) that the Takings Clause “does not distinguish between legislative and administrative land-use permit conditions,” meaning standardized impact fees set by ordinance are subject to the same test as case-by-case exactions.5Justia U.S. Supreme Court. Sheetz v. El Dorado County, 601 U.S. 267 (2024) If a dedication demand is disproportionate to what your subdivision will actually generate in demand, that is a defensible ground to push back.
Recording the Plat
Once approved, the surveyor or a designee records the plat with the recorder in the county where the land sits. In counties with a population of one million or more, the person recording the plat must also deliver six true copies to the recorder.
County recorders will refuse plats that fall outside the required dimensions (at least 8.5 by 14 inches, no larger than 30 by 36 inches) or that lack required approvals. More consequential is this: the recorder cannot record deeds or leases that attempt to convey property in violation of the Plat Act.6Illinois General Assembly. Illinois Code 765 ILCS 205 – Plat Act If the recorder has any doubt about compliance, they can require an affidavit proving the transaction is exempt. The practical effect is that noncompliant lots cannot be sold, because no deed will record.
Penalties for Skipping the Plat Process
The Plat Act backs its requirements with a layered set of penalties:6Illinois General Assembly. Illinois Code 765 ILCS 205 – Plat Act
- Selling or leasing a lot for more than five years before the Act’s requirements have been met is a petty offense with a $25 fine per lot sold or leased.
- Surveying land in a manner that does not follow the Act, or failing to place required corner monuments, is a petty offense with fines between $25 and $100.
- Destroying or removing a survey marker is a Class A misdemeanor.
- County recorders cannot record deeds or leases conveying property in violation of the Act.
- Counties with building permit authority can deny permits for any improvement on a parcel subdivided contrary to the Act.
- When the recorder discovers a violation, the recorder must notify the State’s Attorney, who is then required to prosecute.
- A party who continues to refuse compliance after conviction faces a new petty offense charge for every month the violation persists. Half of any recovered fine goes to the county; half goes to the person who reported the violation.
The Act does allow a developer to accept deposits and offers before compliance is complete, as long as no deed is conveyed until the requirements are satisfied. Municipalities can also issue stop-work orders through their zoning inspectors to halt construction until violations are corrected.
Appealing a Denial
If the municipality or county denies your plat, you can seek review in circuit court under the Illinois Administrative Review Law. The deadline is tight: file a complaint and have summons issued within 35 days of receiving the denial decision.7Justia Law. Illinois Code 735 ILCS 5 Article III – Administrative Review Miss it and the right to appeal is gone. The case can be filed in the circuit court of any county where part of the hearing took place, where the land is located, or where the underlying transaction occurred.
Court review is not a fresh hearing. You cannot present a new plat or new engineering. The judge examines the administrative record to decide whether the approving body followed its own rules and had a rational basis for the denial. The developer carries the burden of showing the decision was arbitrary, unreasonable, or unsupported by the evidence, and the standard generally favors the municipality’s judgment on planning questions. Procedural missteps during the hearing, inconsistency with the local ordinance’s own language, or a disproportionate exaction under Nollan, Dolan, and Sheetz are the strongest angles.
If your project is close to the five-acre line, involves any new access road, or sits near a municipal boundary, have a surveyor and a local land-use attorney check the trigger and the approving body before you spend money on engineering. Those two early calls prevent most of the expensive mistakes.