Job costing means every dollar you spend gets assigned to the job it belongs to. Not dumped into general categories like “materials” or “labor” where it disappears into the monthly P&L. Assigned to a specific project so you can see whether that kitchen remodel in the Fan made money or just kept you busy.

Start with a job numbering system. Every project gets a unique identifier. Use it on timesheets, purchase orders, subcontractor invoices, equipment logs. Every piece of paper that represents money going out should have a job number on it. No exceptions. The system doesn’t work if you’re assigning costs after the fact based on memory.

Labor is usually the hardest to track and the most important. Your crew doesn’t naturally think about which job they’re working on hour by hour. They show up, do the work, go home. You need a system that captures hours by job without creating paperwork that nobody fills out. Daily time sheets by job work if someone actually collects them. Apps like Busybusy or ClockShark work better for most contractors. The goal is accurate hours tied to jobs with minimal friction.

Materials tracking requires discipline at the purchase stage. When someone runs to the supply house, the receipt needs a job number. When you order from a supplier, the PO needs a job number. When the invoice arrives, it gets coded to the right job. If materials go to the shop and then get distributed to multiple jobs, you need a way to track that allocation. This is where most contractors get sloppy and job costing falls apart.

Subcontractor costs are the easiest to track because subs invoice you by project. Make sure every sub invoice gets coded to the correct job before it’s paid. If a sub works on multiple jobs in one invoice, break it out. The few minutes this takes saves you from meaningless job cost reports.

Equipment is trickier. If you own a skid steer and it bounces between three jobs in a week, how do you allocate the cost? Most contractors either track equipment hours by job and apply an internal rate, or they allocate equipment costs based on labor hours. Pick a method and use it consistently. Inconsistent allocation makes job-to-job comparisons worthless.

Overhead allocation is where people overthink it. Your office rent, insurance, truck payments, and your own salary have to come from somewhere. Some contractors allocate overhead to each job based on a percentage of direct costs. Others don’t bother and just look at direct job profitability, knowing overhead comes off the top of overall gross profit. Either approach works. Just understand what your job cost reports are telling you.

Your accounting software needs to support job costing. QuickBooks Online Plus and above has project tracking. QuickBooks Desktop Contractor is built for this. Sage, Foundation, and Buildertrend are options for larger operations. The software should let you run reports showing costs versus budget by job, profit margins by job, and work in progress across all open jobs. If you’re tracking jobs in spreadsheets separate from your accounting, the numbers will drift apart and you won’t trust either one.

Set up cost codes within each job if you want useful detail. Break out labor, materials, subs, equipment, and permits at minimum. More detailed breakdowns like framing labor versus finish labor or rough electrical versus trim help you see where estimates are off. But don’t create so many codes that people stop using them consistently.

Compare estimated costs to actual costs on every job. This is the whole point. You bid a bathroom remodel at $18,000 in labor, $12,000 in materials, and $6,000 in subs. Did you hit those numbers? If labor ran $22,000, why? Was the estimate wrong or did something go sideways on the job? You can’t bid the next one better if you don’t know what happened on the last one.

Run work in progress reports regularly. On longer jobs, you need to know whether you’re ahead or behind before the project ends. If you’ve billed 60% of the contract but spent 75% of the budget, you’ve got a problem. Catching this at month three gives you options. Catching it at project close just gives you regret.

The contractors around Richmond who stay profitable long-term all have one thing in common: they know their numbers by job. They can tell you which project types make money and which ones look good but bleed margin. They adjust bids based on actual historical data instead of gut feel. That knowledge comes from job costing done consistently over time.

Setting this up takes effort. Maintaining it takes discipline. Most contractors try once, let it slip, and go back to guessing. If you want help building a system that actually sticks, that’s part of what construction bookkeeping should include. The books exist to help you run the business, not just file taxes.