By Tammy Hoang, QuickBooks ProAdvisor | Construction Cost Accounting | (949) 889-3283 Job costing is the most important accounting method in construction — and the one most often done wrong. When job costing is set up correctly and maintained monthly, a contractor knows exactly how much every active project has cost to date, how that compares to the original budget, and what the projected margin is at completion. When it is not set up correctly, a contractor knows their bank