Build a Rolling 13-Week Cash Forecast

A rolling 13-week forecast shows how cash may move over roughly a quarter while preserving enough detail to identify a difficult payroll or supplier week. Thirteen weeks is a chosen planning horizon, not a guarantee of accuracy. The near weeks can rely on dated invoices and commitments; later weeks usually need assumptions that should be identified separately.

Establish the opening balance and first weeks

Start with $18,000 of hypothetical usable opening cash. Week one has $7,000 of receipts and $10,000 of payments, leaving $15,000. Week two receives $4,000 and pays $12,000, leaving $7,000. Week three receives $11,000 and pays $8,000, ending at $10,000. Every week's closing balance becomes the next week's opening balance.

If the business chooses an $8,000 minimum operating cushion for this example, week two is $1,000 below that cushion. It is not a negative bank balance, and the cushion is not an expense. Keep separate columns for cash and distance from the selected minimum so the warning is interpreted correctly.

Build the forecast from supporting schedules

Use an invoice collection schedule for receipts, a vendor calendar for supplier payments, and known payroll, rent, subscription, and equipment dates for outflows. Include only cash movements. Depreciation belongs in the profit model, while a paid equipment purchase belongs in the cash schedule. Avoid putting both the full purchase and depreciation into payments.

Record confirmed commitments separately from estimated future spending. That distinction helps identify what can be changed if a shortfall appears. A forecast is less useful when every row is a single percentage of sales, because it conceals large bills and the actual flexibility in the plan.

Roll forward and preserve the evidence

At week end, replace that week's estimate with actual receipts and payments, reconcile closing cash, and add a new week thirteen. Save the previous forecast before updating it. Compare the missed receipts and unexpected payments with the original assumptions, then change future weeks only when new information supports the change.

If a $3,000 receipt shifts from week two to week four, remove it from week two and add it to week four; do not merely add the later receipt. Retain a negative projected balance if one occurs. It represents an unresolved cash gap, not permission to spend unavailable money. A weekly forecast can still hide a shortage within the week, so inspect exact dates whenever the week's lowest likely balance is close to the operating cushion.

Method references: OpenStax: Prepare Financial Budgets. Accessed October 22, 2026. All dollar figures are hypothetical worked examples.