Every contractor tracks costs. Materials, labor, subs — it all gets logged somewhere, whether that's a spreadsheet, an accounting system, or a notebook in the truck. But tracking costs and actually understanding job profitability are two different things. Most contractors do the first. Far fewer do the second.
Here are the five mistakes that keep job costing from being useful.
1. Tracking costs but not allocating overhead
Materials and labor are straightforward to assign to a job. You bought lumber for the Smith project, so it goes on the Smith project. But what about equipment depreciation? Insurance? Fuel for the trucks? Office rent? Shop utilities?
These costs are real, and they eat into every job's margin. When overhead gets dumped into one general bucket instead of allocated across active jobs, your job cost reports look better than reality. A job that shows a 25% margin might actually be running at 12% once you account for the overhead it consumed. If you're bidding future work based on inflated margins, you're setting yourself up for trouble.
2. Ignoring change orders in the accounting
The scope changed. The client added a wall, moved a door, upgraded the finish package. The price went up — or at least it should have. But in the books, the job still shows the original bid amount.
Change orders need to hit the job cost report. Both sides of them — the additional revenue and the additional cost. If your accounting only reflects the original contract, you're making decisions on stale data. And when the job closes out, the numbers won't reconcile with what actually happened.
3. No WIP schedule
A work-in-progress schedule compares how far along a job is with how much you've billed and how much you've spent. Without one, you can't see over-billing or under-billing — and both are problems.
A job that looks profitable on paper might be significantly overbilled, meaning you've collected revenue you haven't earned yet. When the remaining work gets done, that margin evaporates. On the flip side, under-billed jobs tie up cash and hide the fact that you're financing the client's project out of your own pocket. A WIP schedule catches both of these before they become surprises.
4. Waiting until the job is done to review costs
Job costing is only useful if you look at it while you can still do something about it. A post-mortem on a finished job tells you what went wrong, but it can't fix the problem. A mid-job review can.
Monthly job cost reviews — bi-weekly on larger projects — let you catch labor overruns, material waste, and scope creep early enough to adjust. If a job is running 15% over budget at the halfway mark, you have options: tighten up crew management, renegotiate the scope, or at least stop the bleeding. If you wait until the job is done, all you have is a lesson for next time.
5. Using one system for bidding and another for tracking
The estimate lives in a spreadsheet. The costs live in QuickBooks. Nobody is comparing the two in any systematic way. Maybe someone eyeballs it at the end of the job, but by then it doesn't matter.
Budget vs. actual comparison needs to be automatic — or at least routine. If your estimating tool and your accounting system don't talk to each other, build a simple bridge: export your bid breakdown into your job cost structure so you can track actual costs against what you expected to spend. Without that comparison, you're flying blind on every bid.
The bottom line
Job costing isn't about tracking expenses — it's about knowing which work makes you money and which work doesn't. Fix the system, and you'll bid smarter, manage tighter, and grow with confidence.
Stoneledger Advisory Group helps contractors in the Brookings area build financial systems that work. Book a free consultation to talk about your job costing.