Prevailing Wage in Illinois: A Contractor's Guide to the Illinois Prevailing Wage Act

Contractors bidding on public works projects in Illinois face a prevailing wage framework that operates independently from the federal Davis-Bacon Act. The ​Illinois Prevailing Wage Act (820 ILCS 130) sets its own rates by county and trade classification, enforces its own filing requirements, and carries its own penalty and debarment provisions. Getting the federal rules right does not guarantee compliance with the state requirements.

The most common source of confusion for contractors new to Illinois public works is the reporting cadence. Where federal Davis-Bacon requires weekly certified payroll using Form WH-347, Illinois requires a monthly Certified Transcript of Payroll filed through the IDOL portal. Missing that distinction means filing the wrong report on the wrong schedule.

The guide below covers the Act's core requirements, how the Illinois framework differs from federal prevailing wage law, the certified payroll reporting process, and common compliance mistakes.

What Is the Illinois Prevailing Wage Act

The Illinois Prevailing Wage Act requires contractors and subcontractors to pay laborers, workers, and mechanics employed on public works projects no less than the general prevailing rate of wages for work of a similar character in the county where the work is performed. The Act is codified at 820 ILCS 130 and administered by the ​Illinois Department of Labor (IDOL).

Public works under the Act means all fixed works constructed or demolished by any public body, or paid for wholly or in part out of public funds. The definition covers roads, bridges, schools, government buildings, water and sewer infrastructure, and any other construction project funded with public money at the state, county, or municipal level.

Prevailing wage rates in Illinois are determined at the county level. IDOL publishes current rates for each of the state's 102 counties, organized by trade classification. Rates include two components: the hourly cash wage and the fringe benefit contribution. Contractors must ensure that the total compensation for each worker, wages plus fringes, meets or exceeds the published rate for the applicable county and classification. New rate determinations are typically published each July, and revised rates apply to all projects currently underway as well as future projects.

Contractors must post the applicable prevailing wage rates at the jobsite where workers can see them. The posting requirement applies to every public works project, regardless of size or duration.

One critical distinction: union affiliation has no bearing on coverage. The prevailing wage obligation applies to all contractors and subcontractors on covered projects, whether union or non-union. If the CBA rate is lower than the prevailing rate, the prevailing rate governs.

How Illinois Prevailing Wage Differs From Federal Davis-Bacon

Contractors working on projects that involve both state and federal funding may need to comply with the Illinois Prevailing Wage Act and the ​federal Davis-Bacon Act simultaneously. While the two frameworks share the same basic concept, the operational details differ in ways that affect bidding, payroll processing, and reporting.

The key differences between the Illinois Prevailing Wage Act and federal Davis-Bacon include:

• Rate determination geography: Illinois sets rates by county, with IDOL publishing rates for all 102 counties. Davis-Bacon rates are determined by the Department of Labor for specific project areas and are listed in the contract's wage determination

• Reporting cadence: Illinois requires monthly ​certified payroll submissions through the IDOL portal. Federal Davis-Bacon requires weekly certified payroll using Form WH-347, submitted to the contracting agency

• Rate update timing: Illinois rates are updated regularly, and revised rates apply immediately to ongoing projects. Davis-Bacon wage determinations are typically locked at the time the contract is awarded, unless the contract specifies otherwise

• Coverage trigger: The Illinois Act applies to any public works project funded wholly or in part with public funds, with no minimum dollar threshold. Davis-Bacon applies to federal contracts and federally assisted contracts exceeding $2,000

• Apprenticeship: Under Illinois law, only workers enrolled in a U.S. Department of Labor certified apprenticeship program may be paid at the apprenticeship rate

Effective August 2025, HB 1189 expanded coverage so that the Illinois Prevailing Wage Act may also apply to certain federally funded public works projects. Contractors on dual-funded projects should apply the higher of the two rates where both laws cover the work.

Certified Payroll Reporting Requirements in Illinois

Certified payroll in Illinois follows a monthly reporting cycle, which is different from the weekly cadence that most contractors are accustomed to under federal Davis-Bacon. The monthly report is called the Certified Transcript of Payroll and must be filed electronically through IDOL's ​Certified Transcript of Payroll Portal.

The monthly transcript is generally due by the 15th of the month following the reporting period. Contractors should verify current portal deadlines with IDOL before their first filing on a new project, as submission mechanics may be updated periodically.

Each certified transcript must include worker names, trade classifications, daily hours worked, hourly wage rates, fringe benefit payments, gross pay, and a signed compliance statement. The format is prescribed by IDOL and differs from the federal WH-347 form. Contractors who are filing both state and federal ​certified payroll on the same project need to maintain two parallel reporting workflows.

Monthly filing does not mean monthly recordkeeping. Contractors must maintain weekly time and payroll records regardless of the monthly submission schedule, and IDOL requires retention for five years.

In addition to filing with IDOL, contractors must also submit certified payroll records to the public body in charge of the project at monthly intervals. Both the general contractor and every subcontractor on a project carry independent filing obligations.

For contractors who also work on public projects in other states, the Illinois monthly cadence is a significant operational difference. ​California requires electronic certified payroll submission to DIR, and ​New York has its own certified payroll requirements with different forms and submission rules. Managing multi-state compliance requires a payroll system that handles each state's format and schedule natively.

Common Illinois Prevailing Wage Compliance Mistakes

Even experienced contractors make compliance errors when working on Illinois prevailing wage projects, especially when transitioning from federal-only work or from projects in other states. The most frequent mistakes tend to involve rate application, reporting format, and apprenticeship rules.

Common compliance mistakes on Illinois prevailing wage projects include:

• Using outdated wage determinations, particularly after IDOL publishes revised rates that apply immediately to ongoing projects, not just new contracts

• Applying the wrong county rate when a project spans multiple counties, or when workers travel between jobsites in different counties during the same pay period

• Filing a federal WH-347 when the project requires the Illinois Certified Transcript of Payroll format, or filing the state report on a weekly schedule instead of monthly

• Paying apprenticeship rates to workers who are not enrolled in a U.S. DOL certified apprenticeship program, which violates the Act regardless of the worker's skill level or experience

• Missing the fringe benefit calculation, where the total hourly determination includes both the cash wage and the fringe component, and any fringe not covered by employer-paid benefits must be added to the cash wage

• Failing to submit certified payroll to both IDOL and the public body, since both submission obligations exist independently

Violators of the Illinois Prevailing Wage Act are required to pay workers the difference between the wage paid and the prevailing wage. Contractors may also face penalties, punitive damages, and potential debarment. A contractor or subcontractor found to have violated the Act on two separate occasions may be prohibited from public works projects for four years and placed on the IDOL debarment list, which is published quarterly in the Illinois Register. A conviction under Section 5 or 6 of the Act triggers automatic and immediate debarment with no right to a hearing.

How Trayd Supports Illinois Certified Payroll

Managing Illinois prevailing wage compliance alongside federal and multi-state reporting requirements demands a payroll system that understands the differences between each framework. A platform designed for general payroll will not generate an Illinois Certified Transcript of Payroll in the format IDOL requires, and manually formatting reports each month introduces errors and consumes hours that could be spent on higher-value work.

Trayd's ​certified payroll platform is built for the complexity of multi-state and multi-framework compliance. County-level prevailing wage rates, fringe benefit tracking, and certified payroll generation are handled within the same system that processes payroll, tracks field hours, and manages job costing. When rates change, the system applies the updated determination from the effective date forward, reducing the risk of using outdated rates on active projects.

For contractors working across Illinois and other prevailing wage states, Trayd handles each state's reporting format and submission cadence within a single platform, eliminating the need to maintain separate reporting workflows for each jurisdiction.

Schedule a Demo to see how Trayd handles Illinois certified payroll and prevailing wage compliance for trade contractors.

Frequently Asked Questions

Who is covered under the Illinois Prevailing Wage Act?

All laborers, workers, and mechanics employed on public works projects in Illinois are covered, regardless of whether the contractor or the worker is union-affiliated. The obligation applies to every tier of the contractor chain, from the general contractor through all subcontractors performing work on the project.

How often must certified payroll be submitted in Illinois?

Certified payroll in Illinois is submitted monthly, not weekly. The Certified Transcript of Payroll is generally due by the 15th of the month following the reporting period, filed electronically through the IDOL portal. Contractors must also submit certified payroll to the public body overseeing the project at monthly intervals.

What are the penalties for prevailing wage violations in Illinois?

Violators must pay workers the difference between the wage paid and the prevailing wage, and may face additional penalties and punitive damages. A contractor found to have violated the Act on two separate occasions may be debarred from public works projects for four years. IDOL publishes the debarment list quarterly.

Do non-union contractors need to pay prevailing wages in Illinois?

Yes. The Illinois Prevailing Wage Act applies to all contractors and subcontractors on public works projects, regardless of union affiliation. A non-union contractor bidding on an Illinois public works project must pay workers at least the published prevailing rate for the applicable county and trade classification.

Where can I find current Illinois prevailing wage rates?

IDOL publishes prevailing wage rates for all 102 Illinois counties on its website. Rates are organized by county and trade classification, and new determinations are typically published each July. Contractors should check the IDOL website before bidding and again before each pay period to confirm the applicable rate has not been revised.

Does the Illinois Prevailing Wage Act apply to federally funded projects?

Beginning August 2025, HB 1189 expanded the Act's coverage to apply to certain federally funded public works projects. Contractors on projects with both state and federal funding should determine which rate, Illinois prevailing wage or Davis-Bacon, applies to each trade classification and pay the higher of the two where both frameworks cover the work.