A WIP report is the accountant's view of job costing: one row per open job, with the contract value, the estimated total cost, the cost to date, the percent complete (cost to date divided by estimated cost), the revenue earned (percent complete times contract) and the amount billed. The last two columns are the point. Billed more than earned, you're overbilled and holding the client's money; billed less, you're underbilled and financing the job yourself. Bonding companies and banks ask for it; small contractors rarely produce it, and their year-end profit swings when the accountant finally does.
A worked number
Contract $120,000, estimated cost $90,000, cost to date $45,000: 50% complete, revenue earned $60,000. Billed to date $72,000: overbilled by $12,000, which is a liability, not profit. Billed $50,000: underbilled by $10,000, which is revenue you've earned and haven't asked for.
The mistake it hides
A percent complete built on a stale estimated cost. If the job is going to cost $100,000, not $90,000, the percent complete drops to 45% and the "earned" revenue with it. The WIP is only as good as the estimate at completion feeding it.
In Obra
Obra keeps the per-job inputs a WIP needs current: contract plus change orders, recorded cost, the reviewed remaining to spend, expected final cost and cash collected. Export them and the report is a spreadsheet away; the QuickBooks guide covers the accountant handoff.