Certified Payroll in Illinois

If you're a contractor or subcontractor on an Illinois public works job, certified payroll in this state has one twist that surprises everyone coming from the federal system: the state filing is monthly, not weekly, and it goes through an online portal run by the Illinois Department of Labor. That doesn't make Illinois easier — you still keep weekly records, you still have to pay the right county rate, and on federally funded work you may owe a weekly WH-347 on top of the state transcript. This guide walks through how it all fits together.

Who's covered: the Illinois Prevailing Wage Act

Illinois prevailing wage requirements come from the Illinois Prevailing Wage Act (820 ILCS 130), not the federal Davis-Bacon Act. The Act covers construction of public works — projects built, repaired, or maintained for a public body, whether that's the state, a city, a county, a school district, or another unit of government. If a public body is paying for the construction work, assume the Act applies until someone with authority tells you otherwise, and get that in writing. The Illinois Department of Labor (IDOL) administers the Act, publishes the prevailing rates, and enforces compliance. The official source for rates, portal access, and current guidance is labor.illinois.gov.

The big Illinois difference: monthly filing through the CTP Portal

On covered public works, contractors and subcontractors must file a certified transcript of payrollelectronically through IDOL's Certified Transcript of Payroll (CTP) Portal. The cadence is monthly: the transcript for a month's work is generally due by the 15th of the following month. Portal mechanics and deadlines can change, so confirm current portal rules with IDOL before your first filing on a new project.

Two things about this trip people up. First, monthly filing does not mean monthly record-keeping. You still track hours, classifications, rates, and deductions week by week — the monthly transcript is built from those weekly records, and auditors will want to see them. Second, the obligation runs for the duration of the project: every month you have workers on the job, a transcript is due.

Federal overlap: when the weekly WH-347 also applies

Here's the part that catches subcontractors on infrastructure and transit work: if your Illinois project receives federal funding, Davis-Bacon requirements can apply alongside the state Act — and Davis-Bacon means a weekly certified payroll, typically on Form WH-347, submitted to the contracting agency. The two obligations don't cancel each other out. Both can apply to the same job: a weekly WH-347 for the federal side and a monthly CTP transcript for IDOL. When both apply, workers are owed the higher of the applicable rates for their classification. Your contract documents say which funding streams are in play — read them, and ask the public body or prime contractor if it's unclear.

Finding the right rate: IDOL county schedules

IDOL publishes prevailing wage schedules by county and by trade. The applicable rate is the one for your project's countyand each worker's classification — a laborer in Cook County and a laborer in a downstate county can be on very different numbers. Each classification carries a base hourly rate plus fringe benefit amounts, and rates are updated over time, so pull the schedule in effect for your project rather than reusing numbers from a past job. If a worker performs work in two classifications in the same period, record the hours separately at each rate. When in doubt about which classification fits the work, verify with IDOL or your public body before you certify anything.

Penalties: why this is worth getting right

Violations of the Prevailing Wage Act carry real consequences: back wages owed to workers, monetary penalties, and — for repeat violators — debarment from public works contracts. And because the certified transcript is signed as true and accurate, filing a transcript you know to be wrong is its own problem, separate from the underpayment itself. The exposure compounds monthly for the life of the project, which is exactly why catching a rate or fringe error in month one beats discovering it in an audit after month twelve.

Common Illinois mistakes

• Treating monthly filing as monthly record-keeping. The transcript is monthly; the underlying payroll records are weekly. Loose weekly records make an accurate monthly filing nearly impossible.
• Missing the federal overlap. Assuming the IDOL transcript covers you on a federally funded job — and skipping the weekly WH-347 the contracting agency expected.
• Using the wrong county's rates.The rate comes from the project county, not your office's county or a schedule you saved last year.
• Shorting the fringe. The required package is base plus fringe. If your cash wage plus bona-fide benefit contributions falls short of the total, the gap becomes back wages across every hour worked.
• Stopping too early. The filing obligation runs as long as you have workers on the project — not just for the busy months.

How Certiwage helps

Certiwage generates a clean, weekly WH-347certified payroll report from your crew's hours and rates, with the Davis-Bacon overtime formula applied correctly and a fringe checkthat compares your cash-plus-benefits package against the required rate before you sign. Because you enter everything weekly, its records also give you the worker, classification, hours, rate, and deduction detail the monthly Illinois transcript asks for — you submit per your contract and IDOL's portal requirements. Certiwage is a document-preparation tool, not legal advice, and it is not affiliated with IDOL or the U.S. Department of Labor, so confirm your project's specific filing requirements with IDOL or your public body. You can compare how other states handle it in our California and New Jersey guides.

The fastest way to see your numbers checked is to run one week through the free WH-347 builder — no signup, and the fringe and overtime math is verified for you.