Payroll Compliance Small Business
Certified Payroll for Illinois Public Works: What Contractors Actually Have to File
Published August 26, 2026 by Invisible LLC Team · 9 min read
You bid the job, you won the job, and you looked up the rates. That was the easy part, and it is the part everybody researches.
Then the first pay application goes in, and somebody asks for your certified payroll. If the answer is "my what," or if it is "sure, give me a week," you have just introduced a delay into your own draw — on a project where the margin was already thin enough that you sharpened the pencil to win it.
You are a contractor, not a payroll clerk. But on public work, the payroll record is part of the deliverable, and it is the one that gates payment.
The short version
Illinois public works contractors file a Certified Transcript of Payroll with the Illinois Department of Labor every month, by the 15th, covering the prior month's work. If the project also carries federal funding, you separately file a weekly certified payroll under Davis-Bacon rules. Those are two different filings on two different clocks, and a lot of contractors discover the second one late.
Records have to be kept for five years, and the certification you sign is a sworn statement — not a formality.
Two filings, two clocks
This is the single biggest source of confusion, so it is worth getting straight before anything else.
Illinois state and local public works are governed by the Illinois Prevailing Wage Act, 820 ILCS 130. Under that Act, certified payroll goes to the Illinois Department of Labor through an online portal, monthly.
Federal or federally assisted construction contracts over $2,000 are governed by the Davis-Bacon and Related Acts. Under those rules, certified payroll goes to the contracting federal agency, weekly.
A project can be subject to one, the other, or both. A municipal water main funded partly through a federal program is a common example of both — and if you file only the Illinois monthly transcript on that job, you are missing a federal obligation that has been accruing weekly since you mobilized.
Before you run payroll on a new public job, get a straight answer to one question: what is the funding source? The answer determines your filing calendar, and it is much cheaper to ask the awarding body in week one than to reconstruct twelve weeks of weekly payrolls in month four.
The Illinois filing: monthly, by the 15th
Illinois moved certified payroll reporting to a state-run online system under Public Act 100-1177, codified at 820 ILCS 130/5.1. Here is how it works in practice.
Where it goes. You file through the Illinois Department of Labor's Certified Transcript of Payroll portal at webapps.illinois.gov/DOL/PayrollCertification/. Access requires an Illinois Public ID account, which is worth setting up before your first filing is due rather than on the 14th.
When it is due. The certified transcript for the immediately preceding month is due no later than the 15th day of each calendar month. Work performed in September is filed by October 15.
Bulk filing. IDOL publishes an Excel template for importing payroll data into the portal, which matters enormously if you are running more than a handful of workers across multiple classifications. Hand-keying a fifty-employee month into a web form is how errors get made.
The public body still gets records too. Filing with IDOL does not erase your obligation under Section 5 of the Act to keep records available to the public body awarding the contract and to the Director of Labor. Many awarding bodies have their own submission requirements written into the contract documents on top of the state filing. Read the contract — the state minimum is a floor, not a ceiling.
If you are still working out which rates apply to which classification on your job, start with our guide to Illinois prevailing wage rates — rate schedules are published by county and change during the year, so the schedule in effect for the work period is the one that governs.
The federal filing: weekly, within seven days
If Davis-Bacon applies, the clock is much tighter.
Under 29 CFR 5.5(a)(3)(ii), covered contractors and subcontractors must submit certified payrolls weekly, and each one is due within seven days after the regular payment date for that payroll period. They go to the federal contracting agency if it is a party to the contract — or, if it is not, to the applicant, sponsor, or owner maintaining the records for transmission to the federal agency that provided the assistance.
One useful clarification: Form WH-347 itself is optional. The Department of Labor provides it for convenience, and a properly completed WH-347 satisfies the reporting requirements. But you are free to submit the same information in another format. What is not optional is the weekly submission and the signed statement of compliance that accompanies it.
Most contractors just use the WH-347. It is free, it is what reviewers expect, and using the standard form removes an entire category of "your format is missing a column" correspondence.
What actually has to be in the record
Illinois requires contractors and subcontractors on public works to make and keep records showing, for each laborer, worker, and mechanic:
- Name and address
- Telephone number
- The last four digits of the Social Security number
- Classification (this is where prevailing wage lives — the rate follows the classification)
- Hours worked each day, including starting and ending times
- Hourly wage rate and gross wages
- Itemized deductions
- Net wages paid each pay period
Fringe benefits need their own treatment. If you pay fringes into a bona fide plan rather than as cash on the check, IDOL provides a Fringe Benefit Affidavit to document it. If you cannot substantiate the fringe contribution, the safe assumption is that the reviewer will treat the fringe portion as unpaid — and the exposure is the difference, across every hour, for every worker.
Each monthly transcript carries a signed statement of compliance certifying that workers were paid the prevailing rate and classified correctly. Sign that carefully. It is an attestation, not a cover sheet.
Where certified payroll actually goes wrong
In our experience the errors that hold up payment are almost never exotic. They cluster in five places.
1. Misclassification. A worker performing laborer duties is coded as an operator, or vice versa. Classification drives the rate, so a classification error is a wage error on every hour it touches. When a worker splits time across classifications in a day, the hours have to be split too — not averaged, not assigned to whichever rate is higher.
2. Overtime computed on the base rate only. Prevailing wage work has its own overtime conventions, and the awarding body's contract may impose more. Compute overtime wrong and the transcript is internally inconsistent, which reviewers notice immediately.
3. Apprentices without registration. Apprentice rates are only available for apprentices properly registered in an approved program, and ratio requirements apply. An unregistered "apprentice" is a journeyman for wage purposes, retroactively.
4. Owner-operators and small subs left out. Every contractor and subcontractor on the job files. It is common for a two-person sub to assume the general is covering them, while the general assumes the sub is filing its own. Nobody files, and the gap surfaces during review.
5. Nothing filed for a slow month. If you had covered work in a month, that month gets a transcript. Silence is not a filing, and a gap in the sequence is the first thing an auditor pulls the thread on.
Every one of these is a payroll-setup problem, not a paperwork problem. Fix the classification table and the fringe treatment inside your payroll system once, and the monthly transcript becomes an export instead of a research project.
Records, retention, and the cost of getting it wrong
Contractors and subcontractors on public works must keep these records for five years from the date of the last payment on the contract or subcontract, a retention period that has applied to payments made since January 1, 2014 under Public Act 98-328. That is longer than most general business retention habits, and it means the job you closed out in 2023 still has a live file.
On the enforcement side, Illinois provides for wage restitution and penalties, and a contractor with two violations within five years faces debarment from public works for four years (IDOL). For a firm whose pipeline is meaningfully public work, debarment is not a fine — it is the business.
The practical read: certified payroll is not where you want to be economizing on process. The filing itself is cheap. Reconstructing it under audit, three years later, from a payroll system that was never set up for prevailing wage, is not.
Build the routine once
The contractors who find this painless all did the same thing: they set it up once, at the front of the job, instead of monthly forever.
- Confirm the funding source before the first payroll runs. State only, or state plus federal? That single answer sets your calendar.
- Register for the IDOL portal now, not on the 14th.
- Build the classification table into payroll, with the correct rate and fringe treatment per classification, before week one. Every downstream filing inherits this.
- Capture daily start and stop times, not just total hours. The record requires it, and retrofitting it is impossible.
- Calendar the 15th as a hard internal date, with your own cutoff a few days earlier so a discrepancy has room to get fixed.
- Keep the closed-job files. Five years from final payment.
If your team is running mixed public and private work, the classification and fringe setup is where a payroll provider earns its keep — and it is also where a generic provider will happily hand you a system that cannot produce the record you need.
Getting help with it
We handle payroll for contractors and trades running prevailing wage alongside private work — classification setup, fringe treatment, the monthly transcript, and the reporting that keeps the awarding body's questions short. That is our payroll and benefits service, and when you need job-level cost reporting to sit alongside it, our business intelligence work builds the reports.
If certified payroll is currently living in a spreadsheet and a lot of hope, request a quote and we will look at how your payroll is configured before the next filing is due.
This article describes filing requirements as of August 2026 and is general information, not legal advice. Prevailing wage rate schedules change during the year and contract documents may impose additional requirements — confirm specifics with the Illinois Department of Labor and your awarding body.