A 13-week cash flow forecast estimates when money will enter and leave the business over the next thirteen weeks. Build it around expected payment dates, then compare it with actual cash each week. It is a planning estimate, not a promise that the projected balance will be available.
Set up the weekly view
Use thirteen dated columns in your spreadsheet or finance system. Include opening cash, receipts, payments and closing cash for each week. Keep the calculation consistent: opening cash plus receipts minus payments equals closing cash. The next week’s opening cash takes the previous week’s closing balance.
Business.govt.nz’s cash flow forecasting guide describes these core inputs. For this shorter weekly model, add notes that explain the timing and source of material amounts.
Confirm the starting cash
Choose a clear start date and reconcile the accounts included in the model. Identify restricted funds separately from cash available for ordinary operations. Do not count an undrawn credit facility as cash in the bank; show any planned financing as a separate, uncertain receipt unless it is confirmed.
Place receipts in the week you expect payment
Use open invoices, agreed payment schedules and realistic collection information. An invoice date is not a receipt date. Record disputed invoices and large amounts whose timing needs confirmation.
Avoid counting the same sale once from an invoice list and again from a sales forecast. Separate existing receivables from expected new sales and document how the latter becomes cash.
Map payments from actual commitments
Review payroll, supplier invoices, rent, loan payments, tax schedules, subscriptions and planned purchases with the relevant owners. Put payments in their expected weeks, checking for annual bills or irregular costs that a monthly average could hide.
Distinguish contractual commitments from spending that has not yet been approved. Confirm tax and financing treatment with your accountant rather than assuming an accounting expense always has the same cash timing.
Test what happens when timing changes
Here is a simplified illustration in any consistent currency: opening cash of 20,000 plus receipts of 12,000 minus payments of 15,000 gives closing cash of 17,000. If 8,000 of those receipts arrives a week late, the closing balance becomes 9,000 instead. The sale still exists; the timing changes the immediate cash position.
Keep a base forecast and a downside case for important uncertainties. Show which assumption changed and the first week it creates a problem. Do not quietly move due payments to later weeks just to make the model balance.
Update and explain it every week
Replace the completed week with actual receipts and payments, reconcile closing cash and explain important differences. Roll the view forward by adding another week. Save dated versions so the team can see whether assumptions are improving.
Agree who investigates a shortfall and when to involve your accountant or finance adviser. Review recurring commitments through your subscription inventory, but count a saving only when its amount and effective date are supported.