A contractor can close out the year with a profitable-looking income statement and still have lost money on two or three individual jobs. Traditional bookkeeping tells you how the business performed overall. Construction bookkeeping also has to answer a different question: which individual jobs actually made money? A lot of contractors don’t find out they’ve been missing that second question until a job that looked fine on paper turns out to have quietly lost money.
Here’s what Chicago-area contractors should take away from this article:
- Job costing, not month-end totals, is what tells you whether a specific project actually made money — a healthy company-wide P&L can hide a losing job for months.
- A Work-in-Progress schedule is one of the defining tools of construction accounting, tying job costs, billings, and estimated cost to complete together in a way a standard general ledger can’t.
- Illinois and Chicago layer on additional requirements, including sales tax treatment on materials, certified payroll for public jobs, and city-level business tax registration, that a generic bookkeeping setup typically won’t handle correctly on its own.
Job Costing: The Core of Construction Bookkeeping
Job costing means tracking costs and revenue at the level of the individual project rather than only at the level of the company as a whole. Done well, it goes much further than sorting expenses into “materials” or “subs” for a given job. It also captures labor burden (the payroll taxes, workers’ comp, and benefits layered on top of a crew’s wages), committed costs (subcontracts and purchase orders that are obligated but not yet billed), and the gap between estimated and actual cost as a job progresses. Change orders need the same discipline — an approved change order that never gets added to the job’s contract value will make a profitable job look like it’s losing money, and an unbilled one can quietly erase margin that was actually earned.
Consider two jobs that both bill out around $150,000. Tight job costing shows the company kept a solid margin on one. On the other, underestimated labor hours and an approved change order that never got invoiced meant the job actually lost money. Without job-level tracking, both jobs land in the same revenue bucket, and the losing job doesn’t get flagged until it’s already closed.
Key Takeaway: A healthy month-end P&L can hide a losing job for months, since strong jobs quietly absorb the loss until the losing project closes out and the damage is already done.
Work-in-Progress Reporting: Overbilled, Underbilled, or On Track
A WIP schedule is the report that ties job costing back to where a project actually stands financially at any given point, not just at close-out. For each active job, it lines up the contract value, the estimated cost to complete, costs incurred to date, and amounts billed so far, and from that comparison it shows whether the contractor is overbilled (billed ahead of work performed) or underbilled (work performed ahead of what’s been billed).
Being overbilled isn’t automatically bad, but it means some of that cash on hand is really an obligation to finish work the customer has already paid for. Being underbilled means the company has done the work and fronted the cost, and just hasn’t invoiced for it yet, which is a common and often invisible drag on cash flow. A WIP schedule updated regularly, not just at tax time, is what lets an owner catch a job drifting off track while there’s still time to do something about it. It’s also one of the first reports lenders and sureties review when evaluating a contractor’s financial position, because it shows whether reported revenue and cash collections actually reflect project performance.
Revenue Recognition: Why the Numbers Don’t Always Match
Construction is one of the few industries where revenue generally can’t just be booked when cash comes in. If a CPA’s reported profit and a bonding company’s numbers don’t match what an owner expected, the revenue recognition method is usually why. Under the percentage-of-completion method, revenue is recognized gradually as a project progresses; under the completed-contract method, it’s deferred until the job is substantially finished. Which one applies isn’t a free choice for every contractor — smaller companies may qualify for exceptions under federal tax rules, but the calculation depends on gross receipts across related entities, not just one company, so it’s worth confirming with a CPA rather than assuming.
Retainage and Cash Flow: What Owners Actually Feel
Retainage adds another layer: the 5–10% a customer holds back until completion or warranty is money earned but not yet available, and it needs its own line item rather than sitting inside regular receivables. Contractors also feel a cash timing squeeze that has nothing to do with profitability — payroll goes out every week, suppliers often want to be paid on their own terms, and customer draws can take 45 to 90 days to arrive. Businesses fail from running out of cash long before they fail from being unprofitable, and clean construction accounting is what makes that gap visible before it becomes a crisis.
Illinois and Chicago Add Another Layer
None of these fundamentals are unique to Illinois, but contractors working in and around Chicago run into a few state and local wrinkles on top of them. On sales tax, Illinois generally treats a contractor as the end user of materials permanently incorporated into real estate, which typically means owing use or retailers’ occupation tax on those materials at purchase. The exact treatment can turn on the specifics of the contract and project — including exceptions like an approved Enterprise Zone exemption certificate — so it’s worth confirming with a CPA on a project-by-project basis rather than relying on a blanket rule.
Contractors on public or municipal projects also need certified payroll under the Illinois Prevailing Wage Act. Certified payroll records should reconcile to actual payroll and job costing data, and discrepancies between them are a common area of scrutiny in compliance reviews — which is one more reason job costing needs to be built right from the start, not treated as a side task. On top of that, contractors working in Chicago need to register separately for city business taxes, which run on their own filing schedule apart from Illinois state registration, and a contractor working across the city and several suburbs may have obligations in more than one jurisdiction at once. In practice, these requirements only become manageable once payroll, job costing, and tax reporting are working from the same underlying financial data rather than being tracked separately.
Building Books That Show You What’s Happening While There’s Still Time to Act
If your books can’t tell you which projects are making money before the job is over, they’re not giving you the information you need to run the business. Construction bookkeeping should help you make better decisions while work is still in progress, not just explain what happened after it’s too late to change the outcome. That means job costing built around labor burden and change orders, a WIP schedule that’s updated regularly, retainage and cash flow tracked separately from the numbers that look fine on paper, and Illinois and Chicago compliance built into the system rather than handled as an afterthought.
At Ahlbeck & Cook, we work with construction companies and contractors throughout Chicago and the Midwest to build books around how construction projects actually work, from job costing through tax filing. If your financial statements aren’t giving you a clear read on which jobs are making money, contact us to talk through what your books could be doing for you.
