2/15/26  ·  By Ian McCarthy

7 Mistakes You’re Making with Job Costing (and How to Fix Them Before They Kill Your Margins)

Job costing mistakes contractors make

The $273 Billion Problem Most Contractors Ignore

Until it’s too late to save the business

When Ian McCarthy built his landscape company from $0 to $12+ million in revenue over six and a half years, he didn’t do it by accident. He did it by obsessively tracking one thing most contractors get catastrophically wrong: job costing.

$273B

lost annually by the construction industry to avoidable job costing mistakes

Even more alarming? Twenty-five percent of construction companies face bankruptcy after just two or three incorrect estimates.

Construction project manager reviewing job costing documents

Mistake #1: You’re Tracking Costs After the Job Finishes

The problem: You wait until invoices pile up and the job closes to run your numbers. By then, you’ve already lost money.

The fix: Set a weekly review cadence. Every Monday, sit down and review actual costs against estimates on active jobs.

Mistake #2: You’re Guessing on Material Quantities

The problem: You’re “estimating” material needs instead of calculating them precisely.

The fix: Move from estimating to “exactimating.” Use smart tools that pull real-time pricing data.

Contractor truck tailgate with scattered invoices

Mistake #3: You’re Underestimating True Labor Costs

The problem: You miss the labor burden: payroll taxes, workers’ comp, and insurance. You think you’re paying $25/hr, but it’s actually $38/hr.

The fix: Calculate your true labor burden rate and bake it into every estimate.

Mistake #4: Your Cost Code Structure Is a Mess

The problem: You’re either too broad or too granular.

The fix: Build a clean structure with 50–100 codes max. Group them by major categories like “Hardscape Materials” or “Irrigation Install.”

Construction crew morning briefing

Mistake #5: Field Receipts Disappear Into Truck Consoles

The problem: Crumpled receipts in glove boxes mean your “actual” costs are fiction.

The fix: Implement a systematic receipt capture process (like a mobile app) immediately.

Mistake #6: You’re Misallocating Overhead

The problem: You confuse project-specific overhead with company-wide expenses.

The fix: Review your allocation formulas quarterly to keep them relevant.

Contractor organizing job folders

Mistake #7: You’re Absorbing Change Order Costs

The problem: Scope changes happen, but you aren’t documenting them or getting paid for the extra work.

The fix: Track changes in real time and submit change orders with backup data while you still have leverage.

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