Wilburn CPA

Construction Accounting Basics

Ask most builders which job made the most money last year, and you’ll get a guess based on gut feel — not a number pulled from the books. That gap is job costing, and it’s the difference between running a business that happens to be profitable and one that knows exactly why.

Job costing is the practice of tracking every cost against the specific job that caused it, so you can compare what you estimated to what you actually spent — job by job, not just company-wide.

Why Company-Wide Profit Isn’t Enough

Your P&L can show a healthy profit for the year while one job quietly lost money and another one carried the whole company. Without job costing, those two jobs blend together into a single number that tells you nothing about which type of work, which crew, or which client is actually worth repeating.

Job costing is also what makes your WIP schedule possible in the first place — you can’t calculate percentage complete or catch over/underbilling without accurate, job-by-job cost data behind it.

The Four Cost Categories Every Job Needs

At minimum, every job’s costs should break out into:

• Materials — lumber, fixtures, finishes, and everything else purchased specifically for that job
• Labor — your crew’s time, coded to the job they actually worked, not lumped into a general payroll expense
• Subcontractors — every draw and invoice tied back to the trade and the job
• Other direct costs — permits, equipment rental, dumpsters, and anything else that exists only because this specific job exists

Overhead — office rent, your own salary, insurance, software, marketing — is deliberately left out of job costs. That’s a separate number (see our overhead recovery breakdown), and mixing the two is one of the fastest ways to lose track of whether a job actually pencils out.

Estimated vs. Actual: The Comparison That Matters

A job cost report is only useful next to the original estimate. Say you bid a kitchen remodel at $18,000 in materials. If actuals come in at $23,000, that’s a $5,000 variance you want to catch mid-job — not discover after the final invoice, when there’s nothing left to do but absorb it.

Tracked consistently across enough jobs, this comparison also tells you where your estimating is systematically off — a trade you always underbid, a material category that never lands where you planned — so you can fix the estimate, not just the job.

How Often to Review Job Costs

Job costing works best as a weekly habit that feeds an accurate monthly result, not the other way around. Top-performing firms have project managers hold a short weekly check-in on active job costs, budget-to-actual variances, and any unbilled change orders — catching small overruns while there’s still time to react, instead of finding them at month-end.

That weekly rhythm is what makes the formal monthly close accurate. When your team already knows where change orders stand and what’s left to spend, the numbers feeding your WIP schedule reflect what’s actually happening on the job instead of a rough guess — and that accuracy matters, since a bank or surety may be reading that WIP schedule to gauge your financial health.

Common Mistakes Builders Make

• Coding costs to “the company” instead of the specific job, especially for labor
• Using inconsistent cost codes from job to job, which makes it impossible to compare performance across projects
• Tracking costs in the field (in JobTread or similar software) but never reconciling that data against the accounting system, so the two numbers quietly drift apart
• Reviewing job costs only at closeout, instead of weekly — or monthly at an absolute minimum — while there’s still time to correct course

How to Get Started

Start with a standard set of cost codes you use on every job — materials, labor, subs, and other direct costs, broken down by trade or phase if you want more detail. Apply those same codes consistently, job after job, so the numbers are actually comparable.

If you’re managing jobs in JobTread, you already have a head start — it’s built to track costs, budgets, and change orders at the job level in the field. The piece that usually gets missed is connecting that field data to your accounting system, so job costs, your WIP schedule, and your financial statements are all telling the same story instead of three different ones.

That reconciliation — JobTread (or your field system) to the books, every month — is exactly the kind of work we handle for custom builders and remodelers as part of outsourced accounting and fractional CFO engagements. Book a free discovery call and we’ll take a look at how your job costs are currently tracked.

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