Job costing is a feedback loop: estimate with cost codes, capture costs the same way, forecast the finish, and use the variance in the next bid.
Use the same codes from estimate to closeout
If estimating calls work 'carpentry' but timecards use 'labor' and bills use vendor names, variance analysis becomes guesswork. Keep a short, durable code list.
Track commitments before cash leaves
A subcontract or material order is a cost exposure even before the invoice arrives. Commitments prevent an artificially strong margin early in the job.
Review variance while action is possible
Compare budget, committed, actual, and cost to complete weekly on active jobs. Ask whether the issue is quantity, price, productivity, scope, or coding.