Start by enabling the Projects feature in QuickBooks Online. Go to Settings, then Account and Settings, then Sales. Turn on “Organize all job-related activity in one place” and save. Now you can create projects under any customer and assign transactions to them.

When you enter a bill, write a check, or categorize a bank transaction, you’ll see a Customer/Project field. Pick the right project every time. Materials from the hardware store go to the specific job. Subcontractor invoices go to the specific job. Every expense that relates to a project needs that project assigned or it won’t show up in your job cost reports.

Income works the same way. When you create an invoice, assign it to the project. Progress billings, final invoices, change order billing. All assigned to the project so you can see revenue against costs.

Labor is trickier. QuickBooks doesn’t automatically split payroll costs by job unless you’re using the Time Tracking feature and have it integrated with payroll. Most small businesses either use QBO’s built-in time tracking or import time data from an outside app. Either way, someone needs to record hours by project and make sure that data connects to your job costs. If your crew works on multiple jobs in a day, they need to track time by job, not just total hours worked.

The Project Profitability report is where the value shows up. Run it weekly for active jobs, at minimum monthly. You’ll see income minus costs by project so you can catch overruns before they eat your margin. Waiting until a job is done to check profitability means you find out too late to do anything about it.

Where job costing fails is inconsistent coding. You track religiously for three weeks, then get busy and start dumping expenses into general categories without assigning projects. Two months later your reports are worthless because half the expenses aren’t attached to anything. The system only works if every transaction gets coded correctly, every time.

For construction businesses with complex needs like phase tracking, retention, or work-in-progress reporting, QuickBooks may need workarounds or you might need construction-specific software. Construction job costing requires more detailed tracking than most service businesses, and the right setup depends on how you estimate and bill your projects.

If setting this up feels overwhelming, that’s normal. The mechanics are simple but building the habits is hard, especially when you’re running jobs and don’t have time to stay on top of the books. A San Diego bookkeeping service familiar with job costing can configure your QuickBooks correctly from the start and handle the ongoing coding so your reports actually mean something.