The short answer
Will the business have enough cash over the next 13 weeks?
A 13-week cash forecast estimates cash receipts and payments by week, starting from an available opening cash balance. It helps reveal a shortfall before a monthly income statement does. Keep collections, operating payments, capital spending and financing visible, and update the forecast with actual results.
Forecast cash when it moves
Start with reconciled, available cash at a stated cutoff. Forecast customer receipts from invoices, collection patterns and specific customer information. Schedule payroll, suppliers, rent, taxes, interest, debt principal and capital spending when payments are expected. Restricted cash and uncommitted borrowing capacity should not be treated as freely available cash.
For each week: beginning cash + receipts − payments + financing inflows = ending cash. The next week starts with the previous week’s ending cash. Compare the lowest projected balance with a stated operating cash floor. That floor is a planning assumption, not necessarily a debt covenant.
References: Wall Street Prep: 13-week cash flow model
A profitable business can still miss payroll
The fictional model starts with $100,000. Ordinary weekly receipts are $35,000 and ordinary payments are $40,000. An additional $80,000 customer payment is expected in week 5, and a $100,000 equipment payment is due in week 7. With collection in week 5, the lowest week-end balance is $15,000 in week 13, below a $25,000 operating floor.
If the same $80,000 receipt slips to week 9, week 8 ends at negative $40,000. The business has a $65,000 gap to its $25,000 floor. Cash recovers in week 9, but that does not pay the week 8 obligations on time. The example has no financing plug that silently fills the gap.
Try it yourself
Test a late customer payment
Synthetic 13-week forecast in USD. Weekly receipts/payments are flat except for one additional customer receipt and one equipment payment. No financing is assumed.
| Week | Opening cash | Receipts | Payments | Ending cash | Cash floor |
|---|---|---|---|---|---|
| Week 1 | $100,000 | $35,000 | $40,000 | $95,000 | At / above floor |
| Week 2 | $95,000 | $35,000 | $40,000 | $90,000 | At / above floor |
| Week 3 | $90,000 | $35,000 | $40,000 | $85,000 | At / above floor |
| Week 4 | $85,000 | $35,000 | $40,000 | $80,000 | At / above floor |
| Week 5 | $80,000 | $115,000 | $40,000 | $155,000 | At / above floor |
| Week 6 | $155,000 | $35,000 | $40,000 | $150,000 | At / above floor |
| Week 7 | $150,000 | $35,000 | $140,000 | $45,000 | At / above floor |
| Week 8 | $45,000 | $35,000 | $40,000 | $40,000 | At / above floor |
| Week 9 | $40,000 | $35,000 | $40,000 | $35,000 | At / above floor |
| Week 10 | $35,000 | $35,000 | $40,000 | $30,000 | At / above floor |
| Week 11 | $30,000 | $35,000 | $40,000 | $25,000 | At / above floor |
| Week 12 | $25,000 | $35,000 | $40,000 | $20,000 | Below floor |
| Week 13 | $20,000 | $35,000 | $40,000 | $15,000 | Below floor |
2 of 13 week-end balances are below the stated cash floor. No borrowing has been inserted to fill the gap.
A useful AI workflow
Let the spreadsheet own arithmetic and let AI draft commentary from the checked output. Give it period labels, the computed cash balances, the minimum-cash rule and documented timing assumptions. Require an explicit distinction between a confirmed fact and a proposed action.
- Reconcile opening cash and review the receipts/payment schedule.
- Calculate the forecast and test the timing of major collections.
- Ask AI to identify the lowest week, explain documented drivers and list open questions.
- Verify every stated amount and date against the model.
- Assign a human owner to proposed collection, payment or financing actions.
References: Wall Street Prep: 13-week cash flow model
A prompt you can adapt
Using only the attached synthetic forecast and the listed assumptions, draft a short cash review. State the lowest projected week-end cash, the gap to the operating floor and the weeks below that floor. Explain only drivers supported by the data. Separate confirmed facts, assumptions and possible actions. Cite the week and row for each number. Do not invent financing, assume a lender approval or change the model’s calculations.
Replace synthetic data with real records only in an approved environment. Refresh the forecast each week, compare actual cash movements with the previous forecast, explain material differences and add a new week at the end. A missed collection should not disappear just because the calendar advanced.
One-minute check
Can you explain the difference?
Put it into practice
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Common questions
A few useful clarifications
Is a cash forecast the same as a profit forecast?
No. Revenue can precede collections. Inventory and equipment use cash on different schedules from expense recognition. Debt principal changes cash without being an operating expense.
Should the model automatically borrow to prevent negative cash?
Only when an explicit financing schedule models an available facility and its constraints. This teaching template leaves a shortfall visible so the user can plan an action rather than mistake a plug for available funding.
Sources & scope
Reviewed October 9, 2026. Numerical cases are fictional teaching examples, not current market quotes or individual advice. Assumptions appear beside each calculation. Rules, program requirements and source material can change.
- Wall Street Prep: 13-week cash flow modelShort-term cash forecasting framework. All figures and the AI prompt here are original synthetic teaching examples.
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Practice working capital and 13-week cash
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