How to Build a 13 Week Cash Flow Forecast

A 13 week cash flow forecast tracks the cash you expect to receive and pay each week, starting with your available bank balance. It helps you identify a cash shortfall early enough to change collections, spending, or funding plans. For a founder led business, that weekly view can be more useful for immediate decisions than a monthly profit report.

A strong month on the income statement does not guarantee enough cash on payroll day. The forecast connects each commitment to the week it is expected to leave the bank.

The steps at a glance

1. Start with available cash
2. Place receipts in the week you expect payment
3. Map every significant payment
4. Use a delay scenario to test the plan
5. Make the forecast part of the weekly review

Start with available cash

Use reconciled bank balances at the beginning of the first week. Identify restricted cash separately and exclude it from money available for routine spending. An undrawn credit facility is potential funding, not opening cash. Show any planned draw as a separate receipt only when availability and timing have been checked.

Choose a consistent weekly cutoff. A Friday closing balance makes comparisons easier if payroll and many supplier payments also land on Fridays.

Place receipts in the week you expect payment

List open customer invoices and their expected collection dates. Contractual terms are a starting point, but a customer who regularly pays late should not be treated as an on-time payer without a reason. Keep uncertain new sales separate from confirmed receivables.

Then add recurring receipts, customer deposits, and other known inflows. Identify who will confirm each large payment. If one invoice determines whether payroll is covered, it deserves a collection action as well as a spreadsheet entry.

Map every significant payment

Include payroll, payroll taxes, rent, suppliers, loan payments, insurance, software, and planned equipment spending. Use payment dates rather than the month an expense appears in your accounts. Include periodic bills that are easy to overlook, such as annual renewals.

Closing cash equals opening cash plus receipts minus payments. Each week’s closing cash becomes the next week’s opening cash. Compare the lowest projected balance with the reserve you need, rather than looking only at the final week.

Government small business guidance describes the same mechanics. Business.gov.au explains that a cash flow forecast is an estimate of future sales and costs, built from an opening balance plus expected cash coming in minus cash going out, and that estimated figures should be labelled and explained clearly. Business Queensland adds that a forecast is an estimate only, and that mapping the timing of incoming and outgoing payments as accurately as possible helps limit the variance from actual results.

Sources: business.gov.au: Set up a cash flow statement; Business Queensland: Budgets and forecasts.

Use a delay scenario to test the plan

Illustrative example: a business opens a week with $80,000, expects $45,000 in receipts, and plans $70,000 in payments. Projected closing cash is $55,000. If a $30,000 customer payment slips into the following week, closing cash falls to $25,000.

If management has set a $40,000 minimum operating balance, the delayed-payment scenario creates a $15,000 gap. That does not automatically mean borrowing. It means someone must act on collections, reconsider discretionary spending, or assess available funding before the payment date.

Make the forecast part of the weekly review

Replace the completed week with actual receipts and payments, explain meaningful differences, and add a new week at the end. Assign one person to maintain the forecast and an owner to each action. A recurring collection shortfall should change future assumptions.

Read our guide on how much cash a business should keep when setting the minimum balance. This article provides general business information and does not constitute financial, tax, legal, or investment advice.

Common Questions

Is a cash flow forecast the same as a budget?

No. A budget describes planned performance, while a cash forecast places expected receipts and payments on a timeline. Both can be useful, but they answer different questions.

Why use 13 weeks?

Thirteen weeks covers approximately one quarter while keeping the view detailed enough for weekly payment decisions. It is a planning horizon, not a mandatory standard.

How often should the forecast be updated?

Update it weekly, and sooner if a major receipt, expense, or funding assumption changes.