How to Create a 13-Week Cash Flow Forecast, Step by Step

Step 1: Set the start date and opening balance

Choose a start date — usually the coming Monday — and record the combined balance of your business bank accounts on that date. Use the actual bank balance, not the figure in your accounting software, which may include payments that have not cleared.

Step 2: List expected receipts by week

Go through your open invoices and expected sales. For each, estimate the week the money will actually arrive. Use each customer's real payment history: if a client always pays two weeks late, plan for that.

Be conservative with new or uncertain sales. It is better to be pleasantly surprised than to rely on money that does not arrive.

Step 3: List fixed and recurring payments

These are the easiest to forecast and usually the largest:

• Payroll and payroll taxes, on their actual pay dates.
• Rent and utilities.
• Loan and lease repayments.
• Software subscriptions and insurance.

Step 4: Add variable and one-off payments

Add supplier payments based on their terms, estimated tax payments, planned purchases and anything else you know is coming. Check the last few months of bank statements for items you might have forgotten.

Step 5: Roll the balance forward

For each week, calculate closing cash as opening cash plus receipts minus payments. The closing balance becomes next week's opening balance. Look for the lowest point in the 13 weeks — that is the number that matters most.

Step 6: Set a safety threshold

Decide the minimum balance you are comfortable holding — for example, one month of fixed costs. Any week below that line needs a plan: accelerate collections, delay a discretionary purchase or arrange financing in advance.

Step 7: Review and roll every week

At the end of each week, replace estimates with what actually happened, drop the completed week and add a new week 13. Note where you were wrong and why. Over a few cycles, your forecast becomes remarkably accurate.