How to build a rolling 13-week cash flow forecast

A profit and loss statement records revenue and expenses according to accounting rules. A direct cash forecast tracks when money is actually expected to enter or leave the bank. That distinction matters when customers pay later, payroll is due before a client invoice is collected, or loan payments reduce cash without appearing as a new expense.

1. 1. Start with confirmed cash.

   Use the actual available business bank balance at the beginning of week one. Reconcile it before relying on the forecast.

2. 2. Forecast customer receipts by week.

   Use open invoices, expected payment dates, recurring payments, and realistic collection timing. Revenue earned is not the same as cash received.

3. 3. Schedule every cash payment.

   Include payroll, contractors, suppliers, rent, debt payments, taxes, owner distributions, and irregular annual or quarterly payments.

4. 4. Calculate net movement and closing cash.

   Subtract total payments from total receipts, then add the result to opening cash. Carry that closing balance into the following week.

5. 5. Identify the low points.

   Look for weeks below the cash cushion the business needs, then test specific actions rather than reacting when the balance is already low.

6. 6. Roll it forward.

   Each week, replace the completed week’s estimates with actual cash activity and add a new week at the end so the forecast always covers 13 weeks.

Suppose a business begins a week with $20,000, expects $12,000 in customer receipts, and has $16,000 in payments due. Its forecast closing cash is $16,000: $20,000 + $12,000 − $16,000. That $16,000 becomes opening cash for the next week.

The value comes from repeating that calculation across all 13 weeks and making the timing assumptions visible. A profitable month can still contain a difficult week.

• Customers are paying more slowly, so revenue is recorded before the cash arrives.
• Growth requires payroll, contractors, inventory, or other spending before the related customer receipts arrive.
• Debt principal, owner distributions, or equipment purchases use cash without appearing as ordinary operating expenses on the profit and loss statement.
• Large tax, insurance, or annual software payments land in a different period than the related monthly average suggests.
• More sales are coming from a lower-margin service or a customer mix with longer payment terms.

The forecast helps separate a timing issue from a profitability issue. Those problems may look similar in the bank account but call for different responses.

Review variances between expected and actual receipts, update payment timing, and name the next action when a low-cash week appears. That action might involve collections, spending timing, pricing, financing, or a closer look at margins; the right response depends on the cause.

Hayden CFO Advisory helps owners understand revenue, profit, and cash flow drivers through its CFO Advisory engagement. If the numbers needed for a forecast are not yet reliable, Fractional Controller support may be the right place to begin.