Construction Bookkeeping: Job Costing, WIP & Retainage Explained

Construction bookkeeping is not just regular bookkeeping with hard hats. Contractors run multiple projects at once, each with its own budget, timeline, billing schedule, and profit margin — and the money often arrives months after the costs are incurred. Get the bookkeeping right and you know exactly which jobs make money; get it wrong and a “profitable” year can hide a losing project.

This guide covers what makes construction bookkeeping different — job costing, WIP, retainage, progress billing, and the software that handles it — whether you run the books for your own construction business or serve contractors as a bookkeeper.

Why construction bookkeeping is different

Most small businesses can run on straightforward cash or accrual bookkeeping. Construction can’t, because:

• Work is project-based. Profit has to be measured per job, not just company-wide.
• Costs and revenue are out of sync. You buy materials and pay crews long before the customer pays you.
• Contracts are long and billed in stages. Revenue is recognized over time, not at a single sale.
• Money is withheld. Retainage means you don’t collect the full amount until the job closes.

Job costing: the foundation

Job costing means tracking every dollar of cost against the specific project it belongs to, usually across four categories:

• Labor — wages, burden, and payroll taxes for crew time on that job
• Materials — lumber, concrete, fixtures, anything consumed on site
• Subcontractors — amounts paid to subs for that project
• Equipment & other — rentals, mileage, permits, and direct overhead

With job costing in place you can produce a job profitability report that shows estimated vs actual cost for each project — the single most valuable report a contractor has. In QuickBooks Online or Xero this is done with projects (or class/location) tracking.

Work-in-progress (WIP) and revenue recognition

Because projects span months, construction typically recognizes revenue using percentage-of-completion: you record revenue in proportion to the costs incurred so far against total estimated costs.

A WIP schedule compares, for each active job:

• Total contract value
• Costs incurred to date and total estimated cost
• Percentage complete
• Revenue that should be recognized
• Amount actually billed

The gap tells you whether a job is overbilled (you’ve billed more than you’ve earned) or underbilled (you’ve earned more than you’ve billed). Lenders and bonding companies expect an accurate WIP schedule, so this isn’t optional once you take on larger work.

Progress billing and retainage

• Progress billing — You invoice in stages as the work advances, often on an AIA-style schedule of values (G702/G703 forms) for commercial jobs.
• Retainage — The customer withholds a percentage (typically 5–10%) of each payment until completion. Track it separately as retainage receivable. When you withhold from your own subcontractors, track retainage payable. Never bury retainage inside normal AR/AP, or your aging reports will lie to you.

Setting up the chart of accounts

A construction chart of accounts is built for job costing:

• Separate income accounts by contract type (residential, commercial, service work)
• Direct job costs split into labor, materials, subcontractors, and equipment
• A dedicated retainage receivable and retainage payable account
• WIP asset accounts (costs in excess of billings / billings in excess of costs)
• Indirect costs and overhead kept out of direct job costs

Payroll, subs, and compliance

• Certified payroll — Public and prevailing-wage (Davis-Bacon) jobs require certified payroll reports with specific wage determinations. Get the payroll system set up for this before the first public project.
• Subcontractor management — Collect W-9s up front, track payments for 1099 reporting, and keep certificates of insurance and lien waivers on file.
• Sales/use tax — Rules on materials vary by state and by whether you’re the consumer or reseller; confirm the treatment for each jurisdiction.

Software for construction bookkeeping

• Core ledger: QuickBooks Online or Xero, using projects for job costing.
• Construction-specific add-ons: Knowify, Buildertrend, Foundation, or CMiC for estimating, progress billing, and WIP that sync back to the accounting file.
• Document capture: Dext or Hubdoc for the constant stream of material invoices and receipts. See free tools for bookkeepers and accountants for no-cost options.

Pricing construction bookkeeping

Construction clients take more work than a typical small business — job costing, WIP, retainage, and certified payroll all add time — so they should be priced accordingly. Fixed monthly packages that reflect the number of active jobs and payroll complexity work best. See how to price bookkeeping services for benchmarks and package examples.

Frequently asked questions

How is construction bookkeeping different from regular bookkeeping?

Construction bookkeeping is project-based. Instead of tracking overall income and expenses, you track costs and revenue by job, manage work-in-progress and retainage, and often recognize revenue using percentage-of-completion. Progress billing, change orders, and certified payroll add complexity that standard small-business bookkeeping does not have.

What is retainage in construction accounting?

Retainage (or retention) is a portion of each payment, commonly 5–10%, that the customer withholds until the project is complete. It should be tracked separately as retainage receivable (money owed to you) or retainage payable (money you withhold from subcontractors), not lumped into normal accounts receivable or payable.

What is a WIP schedule?

A work-in-progress (WIP) schedule compares costs incurred and revenue recognized against the total contract for each active job. It reveals whether you have overbilled or underbilled a project, which is essential for accurate financials and for bonding and lender requirements.

What software is best for construction bookkeeping?

QuickBooks Online or Xero handle the core ledger, and job or project tracking lets you cost by job. Growing contractors often add construction-specific tools like Knowify, Buildertrend, or Foundation for job costing, progress billing, and WIP, which sync back to the accounting file.

Related guides

• Choosing a profitable accounting firm niche
• How to start a bookkeeping business
• Other industry guides: ecommerce, nonprofit, real estate, restaurant, and law firm bookkeeping.