Cash is the one thing a growing company can't run out of. Yet forecasting often stays stuck in a founder's spreadsheet long after the business has outgrown it. Here's a practical framework to forecast cash with confidence as you scale.
Why forecasting breaks as you scale
Early on, a simple monthly view works. But as headcount, vendors, and receivables multiply, timing becomes everything. A profitable company can still hit a cash crunch if a large receivable slips a few weeks. Forecasting has to get more granular and more disciplined.
The 13-week cash flow forecast, explained
The 13-week forecast is the treasury standard for near-term liquidity. It projects weekly cash inflows and outflows over a rolling quarter, giving you enough runway to act—collect faster, delay a payment, or draw on a line—before a shortfall becomes a crisis. It's short enough to be accurate and long enough to be useful.
Why most forecasts are wrong before the week starts
Most cash forecasts are wrong before the week even starts—not because of bad assumptions, but because AP and AR teams work on different clocks and nobody reconciles them. AR books revenue when the invoice goes out; AP books expenses when the bill is approved. But cash doesn't move on booking dates—it moves on payment dates, and those are rarely the same.
- On the receivables side: customers pay on their own schedule. A net-30 invoice from a large enterprise customer often pays at 45–55 days. If your forecast assumes 30, you're perpetually overstating near-term inflows.
- On the payables side: approved invoices often sit in a payment queue for days, early-pay discounts go uncaptured, and vendor terms are inconsistently applied across the AP team.
The fix isn't a better spreadsheet—it's better data inputs: pull actual historical days-to-collect by customer segment (not contract terms), track payment-release lag from AP approval to cash out, and build a rolling 13-week forecast that adjusts for these behavioral patterns. Just as important, get AP and AR—the teams closest to the data—into the room with treasury. Accurate forecasting dies in a silo.
Building your first forecast
- Inputs: opening cash, expected receipts (by customer), and disbursements (payroll, vendors, debt, taxes).
- Cadence: update weekly and roll the window forward.
- Owners: assign someone accountable for each line so estimates reflect reality, not guesses.
Direct vs. indirect method
The direct method builds the forecast from actual expected receipts and payments—ideal for short-term operational forecasting. The indirect method starts from projected net income and adjusts for non-cash items—better suited to longer-term, strategic views. Growth-stage companies usually want the direct method for the 13-week and the indirect method for annual planning.
Common mistakes to avoid
- Forecasting revenue instead of collected cash
- Ignoring timing—when cash actually moves, not when it's booked
- Never comparing forecast to actuals (no variance analysis)
- Letting the model go stale between updates
Where AI and automation help
Modern tooling can pull bank and ERP data automatically, flag variances, and even suggest scenarios—turning forecasting from a manual chore into a living decision tool. AI-powered forecasting assistants are especially useful for pattern-based receipt timing.
Need a forecasting model built?
CurvedSpace builds cash flow forecasting models and processes tailored to growth-stage companies. Get in touch and we'll help you see around the corner on cash.