How to Build and Update a 13-Week Cash Flow Forecast
Plan weekly money in and money out, spot cash shortages and update the next 13 weeks as real payments arrive. Follow a made-up workshop example.
A 13-week cash flow forecast asks: will you have enough money to pay bills when they are due? It lists money expected in and out each week, not income earned and expenses incurred under accrual accounting. A profitable contract can still leave you short of cash before the customer pays. This forecast helps you spot that gap early. A profit figure alone does not tell you how much you can spend.
1. Define the cash you can actually use
Choose an as-of date, consistent week boundaries and a currency. Reconcile opening cash to reliable bank information and identify restricted funds unavailable for operating payments. Review outstanding transactions so they are reflected once, not omitted or counted twice.
This fictional Canadian workshop starts on November 2, 2026 with $28,000 in bank funds, including $4,000 restricted from operating use. Opening unrestricted available cash is therefore $24,000. All figures are Canadian dollars. No overdraft or prospective loan is included.
2. Put receipts and payments in realistic weeks
Build receipts from specific invoices, payment commitments and expected settlement dates. Distinguish due dates from dates when funds should be usable. Challenge optimistic assumptions for disputed invoices and irregular payers. An annual sales target divided evenly across thirteen weeks is not a collection plan.
For each large receipt, note the invoice or contract, expected payment date, reason for that date and person doing the follow-up. List excluded items separately, such as an unconfirmed grant or a sale still being negotiated. You can discuss them without treating them as available money. If you group small receipts, explain the group and check that no payment also appears on its own. Count an invoice and its expected deposit as one inflow, not two.
List payments for payroll, suppliers, rent, debt, taxes and planned purchases. Include sales tax in customer receipts where applicable, then show the tax payment once in the week you will send it to the government. Taxes collected are not income. Do not duplicate the tax payment in another cash-out category. State any assumed tax amounts; this forecast does not calculate tax.
3. Read the original weekly case
Each row covers Monday through Sunday. Payments include all planned cash outflows, including a $6,500 tax remittance within the second week's $26,000. This base case has no financing receipts or repayments. These commitments are illustrative assumptions, not a recommended budget.
| Week starting | Receipts | Payments | Closing cash |
|---|---|---|---|
| Nov. 2, 2026 | $18,000 | $22,000 | $20,000 |
| Nov. 9 | $14,000 | $26,000 | $8,000 |
| Nov. 16 | $21,000 | $18,500 | $10,500 |
| Nov. 23 | $12,000 | $23,000 | −$500 |
| Nov. 30 | $26,000 | $19,000 | $6,500 |
| Dec. 7 | $18,000 | $21,000 | $3,500 |
| Dec. 14 | $23,000 | $18,500 | $8,000 |
| Dec. 21 | $10,000 | $16,000 | $2,000 |
| Dec. 28 | $8,000 | $14,500 | −$4,500 |
| Jan. 4, 2027 | $25,000 | $17,000 | $3,500 |
| Jan. 11 | $22,000 | $20,000 | $5,500 |
| Jan. 18 | $20,000 | $18,500 | $7,000 |
| Jan. 25 | $24,000 | $20,500 | $10,500 |
Calculate each closing balance as opening cash plus receipts minus payments; carry it into the next week. Across the period, $241,000 of receipts less $254,500 of payments reduces cash by $13,500. Ending at $10,500 does not remove the earlier shortfalls. Negative balances flag a plan that cannot be executed as written without an identified solution.
4. Investigate the lowest point, not just the finish
Cash first goes negative in the week of November 23 and reaches −$4,500 in the week of December 28. The owner's chosen $5,000 planning buffer highlights other pressure weeks. It is not a universal minimum.
Investigate collections, purchase timing and discretionary spending before the gap arrives. Confirm any earlier customer payment or changed supplier terms. Do not move payroll, tax or other committed payments merely to make a cell positive. Assign actions and confirmation dates. Review daily timing in tight weeks: Friday's receipt cannot fund Monday's payment.
5. Separate uncertainty from approved financing
Keep a base forecast and a clearly labelled downside case. Suppose a $9,000 customer receipt expected in the week of November 16 slips to November 30. The November 16 close becomes $1,500 and the November 23 close becomes −$9,500. When the receipt arrives, the November 30 close returns to the base $6,500, assuming nothing else changes.
A loan is an option to check, not money you can assume will arrive. Show new borrowing, money put in by the owner and loan repayments separately. Note approvals, when funds will be available, fees and conditions. Leave unapproved credit out of the version based on confirmed funds. Still show any cash shortage from operations, even if an approved loan covers it. Borrowing is not money generated by the business's work.
6. Replace one week with actual results and roll
At the end of the first week, actual receipts are $16,500 and actual payments are $22,800. Actual closing cash is $24,000 + $16,500 − $22,800 = $17,700, which is $2,300 below forecast. Receipts contributed a $1,500 shortfall and payments an $800 excess.
Investigate whether differences reflect timing, disputes, estimation errors or new spending. Do not automatically add the receipt variance to next week. Verify what remains collectible and when.
Use $17,700 as the new opening cash, update the remaining assumptions and add the week of February 1–7, 2027 to retain thirteen weeks. If the second week's receipts and payments are unchanged, its revised closing balance is $5,700. Preserve the prior forecast for comparison rather than overwriting the evidence of what you expected.
Use differences to improve specific estimates. If a customer keeps paying a week late, change that customer's expected date instead of adding an unexplained buffer to every receipt. Separate uncertain new sales from payments on existing invoices. Comparing forecasts with results should improve your estimates and follow-up. Do not rewrite an old estimate after payment arrives just to make it look accurate.
7. Make the forecast a decision routine
Review weekly with the person authorized to act. Bring the lowest projected balance, uncertain receipts, upcoming commitments and outstanding decisions. Date assumption changes and distinguish facts from estimates. Explaining the next cash pressure is more useful than a beautifully formatted sheet nobody updates.
Bookwits can help coordinate related tasks, client requests and files. Prepare and review the forecast in your accounting or planning tool. Bookwits does not have a built-in cash-forecasting tool.
Frequently asked questions
Is a 13-week forecast the same as a profit forecast?
No. This forecast follows cash receipts and payments in their expected weeks. Accrual profit follows recognition rules and can include amounts that have not been collected or paid. Use both views for their different purposes.
Can I include a hoped-for loan or tax refund?
Identify it as uncertain and show its assumptions separately. Do not present unapproved financing or an unconfirmed refund as assured available cash. Update the forecast when evidence supports the amount, conditions and timing.
Does a positive weekly closing balance prove every payment is covered?
No. Cash can run short earlier within the week, funds can be restricted and expected receipts can arrive late. Examine daily timing around tight periods and maintain a buffer suited to the business rather than relying only on the final weekly number.