Contractors track job costs by assigning every expense, labor hour, and subcontractor invoice to a specific project in their accounting system. The goal is knowing exactly how much each job actually cost so you can see whether it made money or lost it.

Set up your accounting software with projects or jobs as a tracking dimension. In QuickBooks, this means using the Projects feature or Classes. When you buy materials, pay a subcontractor, or log crew hours, assign that cost to the job where it belongs. No exceptions, no “we’ll figure it out later.”

Break each job into cost categories that match how you estimate. Most contractors use something like materials, labor, subcontractors, equipment, and permits. This structure lets you compare actual costs to your original bid at a useful level of detail. If you just dump everything into one bucket per job, you’ll know you lost money but not why.

Labor tracking is where most contractors fall short. Your crew might work on three different jobs in one week. If all their hours get assigned to one job or lumped into general labor, your job cost data is fiction. Track hours by job daily. Time tracking apps work, paper timesheets work. The method matters less than consistency.

Subcontractor invoices need to hit the right job when you pay them. Subs are often 40-60% of a project’s total cost. If those payments aren’t coded to jobs, you’re missing the biggest piece of your cost picture. Review every sub invoice before payment and make sure it’s assigned correctly in your monthly bookkeeping.

Reconcile job costs weekly, not monthly. A monthly review means you find out about the framing overrun after the house is dried in. Weekly reviews catch problems while you can still adjust. Compare what you’ve spent to your budget and committed costs not yet invoiced.

The payoff is real visibility into profitability. You stop guessing which jobs made money. You start seeing patterns. Maybe you always underestimate electrical, or a certain subcontractor consistently runs over. Your future estimates get more accurate because they’re built from actual cost history, not guesses.

Many contractors and construction businesses across Los Angeles struggle with job costing because they’re too busy running jobs to maintain the discipline it requires. A bookkeeper who understands construction can set up the right tracking structure and keep it current so you get the profitability data without spending your evenings on data entry.