Work in progress accounting is the closest thing a project-based firm has to a lie detector. It tells you whether the work you've delivered matches the money you've billed. When the schedule is accurate, you spot margin slippage in real time. When it's stale, problems hide for months — then surface as a write-down nobody saw coming.
This guide covers the questions to ask of your WIP schedule and the five mistakes that quietly distort it. The goal is a number you can act on, not a spreadsheet you stopped trusting.
What a WIP schedule actually measures
A WIP schedule reconciles three things: work performed, costs incurred, and revenue recognized. The gap between them is your unbilled or overbilled position.
Say you've completed 60% of a $200,000 engagement. You've earned $120,000. If you've only invoiced $90,000, you're $30,000 underbilled — that's cash sitting in WIP, not in the bank. Flip it, and overbilling means you've collected ahead of delivery and owe the work.
The schedule must be accurate and up to date to keep a real pulse on contract status. A WIP report built on last quarter's percent-complete is a guess wearing a number's clothes. The AICPA & CIMA firm practice management resources treat this reconciliation as core financial hygiene for service firms, not a year-end formality.
For project-based teams, this connects directly to how you track project costing and utilization rate. WIP is where those two truths meet the invoice.
The five mistakes that distort project margins
Construction and professional-services teams repeat the same five errors. Each one misstates margin in a way that looks fine until it isn't.
1. Stale percent-complete inputs. Project managers estimate completion from memory, not from hours logged. The fix: pull percent-complete from actual timesheets and milestones, refreshed weekly.
2. Costs booked late. Subcontractor invoices and vendor bills hit the ledger weeks after the work. Your WIP looks profitable because the costs haven't landed. Accrue them.
3. Ignoring change orders. Scope grows, the contract value in your schedule doesn't. You under-recognize revenue and panic at a phantom loss.
4. Treating all hours as billable. Write-offs and non-billable time inflate your earned revenue. The Harvard Business Review breakdown of what professional service firms must do to thrive ties firm health directly to honest measurement of delivered value — not hours logged.
5. No realization adjustment. You bill $100 of work and collect $82. That 18% gap is real. Tracking it is the job of your realization rate, and a WIP schedule that ignores it overstates margin on every project.
Build the schedule from live data, not month-old close
The biggest source of WIP error is timing. Most firms build the schedule from a month-end close that's already four weeks old. By the time you read it, the project has moved on.
The Journal of Accountancy guidance on pricing, billing, and collecting fees makes the point plainly: the longer the gap between work performed and the number you act on, the more revenue leaks. WIP is where that leak starts.
CentSight is the intelligence layer that sits on top of QuickBooks and your bank. It reads your live ledger — synced on demand, as often as every fifteen minutes — so the cost side of your WIP isn't waiting on a close. You connect your accounting software in five minutes, and the data underneath your schedule stays current.
The schedule still needs your percent-complete inputs. But the half built from your books no longer drifts.
The questions to ask every week
A good WIP review is a short list of pointed questions. Run them weekly, per project:
- Is percent-complete based on real progress? Hours and milestones, not optimism.
- Are all costs in? Accrue what's coming.
- Does contract value reflect every change order?
- What's our underbilled position? That's cash you've earned and not invoiced.
- What's our realization rate trending toward?
Lead with the number, then the action. "Project X is $40,000 underbilled — send the invoice this week" beats a three-page variance report. The Clio 2024 Legal Trends Report shows how much firm revenue evaporates between work done and cash collected — a tight WIP review is the first place to close that gap.
Connect WIP to billing and collections
WIP is the front end of your cash cycle. The underbilled balance you find this week becomes next week's invoice and next month's receivable.
That's why your WIP discipline and your collections discipline are the same conversation. An accurate schedule tells you what to bill; a tight accounts receivable playbook tells you how fast that bill turns into cash. If your days sales outstanding is climbing while your WIP underbilled balance grows, you have two leaks feeding each other.
Run the math on your own cycle with the DSO calculator, and track accounts receivable turnover alongside it. The NetSuite breakdown of consulting services KPIs puts these metrics in one frame — because in a service firm, they move together.
For the full picture, the billing management hub and the broader professional services finance pillar tie WIP into pricing, resource planning, and the accounts receivable cycle it feeds.
The takeaway
A WIP schedule earns its keep only when it's current and honest. Stale inputs, late costs, and ignored realization don't just blur the number — they hide margin problems until they're write-downs.
Fix the five mistakes. Pull your inputs from real progress. Build the cost side from live data instead of a month-old close. Then run the same five questions every week.
A fractional CFO costs $8K–$15K a month and answers between partner meetings. CentSight is $95/mo and watches your contract financials continuously, in plain English. If what it surfaces confirms what you already know, you're out $95. If it doesn't, it just found the underbilled work you were about to write off.
