A 13-week cash flow forecast is a week-by-week projection of the cash coming in and going out of your business over the next quarter. You build it by starting with your opening bank balance, forecasting receipts from customers, listing every payment due, calculating the weekly closing balance, and then rolling it forward each week while comparing forecast with actual results.
Profit is an opinion; cash is a fact. Plenty of profitable businesses have failed because they ran out of cash at the wrong moment. A 13-week cash flow forecast is the simplest tool for making sure that never happens to you.
What is a 13-week cash flow forecast?
It's a rolling, week-by-week view of your bank balance for the next quarter. Unlike an annual budget, it's built on actual cash timing — when customers really pay, and when suppliers, payroll and tax authorities are really paid.
Step 1: Start with your opening cash balance
Take the combined balance of all business bank accounts at the start of week one. If you operate in more than one currency — common for businesses trading across the USA, UK, Canada and Europe — forecast each currency separately and convert at a prudent rate.
Step 2: Forecast cash receipts
List expected inflows by week:
- Customer receipts based on outstanding invoices and realistic payment patterns (not just invoice due dates)
- New sales you expect to invoice and collect within the 13 weeks
- Other inflows — loans, investment, tax refunds or grants
Step 3: Forecast cash payments
List every outflow by week:
- Payroll and payroll taxes
- Supplier and contractor payments
- Rent, software subscriptions and utilities
- VAT, GST/HST, sales tax and corporate tax payments
- Loan repayments and interest
- Planned capital expenditure
Step 4: Calculate the weekly closing balance
For each week: opening balance + receipts − payments = closing balance. The closing balance becomes the next week's opening balance. Highlight any week where the balance drops below your minimum safe level.
Step 5: Roll it forward and track variances
Every week, replace the oldest week with actual figures, add a new week thirteen, and compare forecast with actual. Variance analysis is where the real value lies: it shows which assumptions are wrong and makes every future forecast more accurate.
Common mistakes to avoid
- Assuming customers pay on time
- Forgetting quarterly or annual payments such as tax, insurance and renewals
- Mixing up profit and cash, especially for deposits, inventory and capital spending
- Building the forecast once and never updating it
How Avore Solutions can help
Our financial forecasting and budgeting services include 13-week cash flow forecasts, longer-range financial models and monthly variance analysis — and our virtual CFO team can turn the results into clear decisions for your leadership team.
Frequently asked questions
Why 13 weeks?
Thirteen weeks is one quarter. It's long enough to spot a cash shortfall early enough to act — for example by chasing receivables, delaying spend or arranging finance — but short enough to forecast accurately week by week.
How is a cash flow forecast different from a profit forecast?
A profit forecast shows income and expenses when they are earned or incurred. A cash flow forecast shows when money actually moves in and out of the bank. A profitable business can still run out of cash if customers pay late or large payments fall due together.
How often should I update my 13-week cash flow forecast?
Weekly. Each week, replace the oldest week with actual figures, add a new week at the end, and review any variances between what you forecast and what actually happened.