Profit on paper does not pay Friday's payroll. Contractors live and die by the timing of billings, approvals, and the reality of field schedules. A rolling 13-week cash plan gives owners and project teams a view of receipts and disbursements over the coming weeks tied to how work actually unfolds. Unlike an annual budget or a trailing P&L, this model converts your work in progress schedule, backlog, and billing cadence into a weekly cash roadmap. Built right, it highlights financial pressure points before they become missed payment applications or supplier holds, and it turns insights from individual jobs into decisions affecting the entire company.
Tie Cash Forecasting to WIP and Backlog, Not Just the P&L
A useful 13-week model starts with the WIP schedule and contracted backlog, not a generic revenue curve. Use each active job's percentage of completion, committed costs, and billable schedule of values to establish expected invoices and likely receipt dates. Some teams handle this internally; others evaluate a fractional CFO service for contractors when they want a structure designed for their needs without building it from scratch.
Translate backlog into billing milestones by project: mobilization, monthly progress billings, and substantial completion. Flag constraints that change timing, like payment clauses tied to receipt of funds, lien waiver sequences, and retainage release conditions. The WIP tells you where declining margins or unapproved change orders might lurk. Bring those into the cash view as inflows adjusted for risk: approved change orders at 100 percent, submitted at a discount until they clear. The result is a forecast grounded in job realities rather than broad averages.
Convert Progress Billing and Retainage Into Weekly Cash Inflows
Applications for payment rarely convert to cash on the invoice date. Map each GC's approval cycle, cutoff dates, and typical days to fund. Separate base billings from retainage. For example, a drywall subcontractor with 10 percent retainage might bill $200,000 in May, but only $180,000 is collectible in the near term, and the $20,000 sits until completion of the remaining work and final approval. Set expected receipt weeks by customer and project, not by a flat "Net 30." Your AR aging should be tagged by GC, job, and approval status to improve forecast accuracy.
Change orders deserve their own pipeline inside the model: identified, submitted, approved, and billed. Extra work directed by the field and installed this week may not result in cash for six to eight weeks if the paperwork lags. By staging change orders, you can show an optimistic scenario, a base case, and a conservative view. This avoids a common pitfall where a manager assumes "we did the work, cash is coming," while the office knows the change order is still being priced. When forecast and paperwork align, surprises shrink.
Map Payroll, Subcontractor Payment Applications, and AP Terms to Outflows
Outflows are not one big "AP" number. Break them into predictable cycles. Payroll comes weekly or every two weeks, with fringe benefits, union benefits, and certified payroll filings layered on top. Subcontractors typically submit monthly payment applications; your payments may be tied to contractual provisions requiring receipt of funds or negotiated terms. Materials may be Net 30 from major suppliers, but certain items like custom glass or equipment with long delivery times often require deposits. Equipment rentals, fuel cards, and small tools flow on different calendars and should be scheduled accordingly.
Identify tradeoffs explicitly. Paying a concrete supplier early for a 2 percent discount can be smart on a strong cash week, but it can also leave insufficient funds for payroll three weeks later if a large AR receipt slips. Model discounts as optional controls so you can see the true cost of taking them versus preserving a buffer. Do the same for insurance installments, bond premiums, sales and use tax, and quarterly estimated taxes. These obligations with fixed payment dates can collide with mobilizations if they are not visible in the same 13-week window.
Stress Test Scenarios Contractors Actually Face
Once the base 13-week plan is set, challenge its assumptions. Run a scenario where a sitework start slides two weeks because the permit is late. Labor that was supposed to increase on Job A now overlaps with Job B's peak, compressing cash outflows before the first progress billing lands. The model should show the temporary dip, how deep it goes, and the week it recovers. With that picture, you can delay a material release, reassign a crew, or draw on the line of credit in a planned way rather than in a scramble.
Another common test: an owner who pays slowly. Assume one GC extends payment from 30 to 55 days for the next cycle. Watch the ripple through subcontractors, supplier terms, and payroll. Decide which subcontractors can receive partial payments within contractual and legal requirements, whether to accelerate lien waivers for faster funding, or whether to move crews to a job with a faster billing cadence. Scenarios are not academic exercises; they drive job sequencing, change order prioritization, and conversations with banks and sureties about borrowing bases and bonding capacity.
Run the Cadence: Weekly Updates, Monthly WIP, Quarterly Lookbacks
Great models lose their value when they go stale. Establish a simple cadence. Hold a short weekly "cash huddle" with operations and accounting to update receipts, delays, and new commitments. Move actual collections from AR into the model, roll the 13-week window forward, and refresh outflows for approved payment applications, payroll hours, and any new purchase orders. Tie updates to job cost codes so project managers can see how field progress and schedule revisions alter billing forecasts as changes occur.
Layer in a monthly WIP review to verify the percentage of completion, capture declining margins, and ensure your forecasted billings match what will be approved. Every quarter, perform a review of past performance: compare forecasted receipts to actual collections by GC and job. If one customer consistently pays 20 days late, build that into the base model. If change orders from a particular owner clear faster, reflect it. The cadence turns planning performed once into an operating rhythm that steadily improves.
A 13-week cash model anchored in WIP, retainage realities, and billing cadence will not eliminate surprises, but it will make them smaller and reveal them earlier. It helps owners decide when to take discounts for early payment, how aggressively to pursue growth without restricting working capital, and when to call the bank before a financial shortage develops. Some contractors build this discipline internally; others bring in outside support to establish the process and train the team. However you approach it, keep it simple, keep it current, and keep it connected to what is happening in the field.