· 3 min read · By Ramy Hanna, Principal & Founder
Cash flow forecasting: the 13-week model every SME should run
Profit is an opinion; cash is a fact. Here's the rolling 13-week forecast we build with clients — and the three mistakes owners make the first time.
More profitable businesses run out of cash than unprofitable ones run out of profit. The reason is timing: revenue is booked when you invoice, but cash arrives when you’re paid — and the gap is where good businesses get caught. A cash flow forecast closes that gap by showing what’s actually going to land in the bank, and when.
Why 13 weeks?
A quarter — 13 weeks — is the sweet spot. It’s far enough ahead to see a problem while you can still act on it (chase a debtor, delay a purchase, draw on a facility), but near enough that your assumptions are realistic. Annual budgets are for strategy; the 13-week view is for survival and control. The best operators run both.
What goes into the model
A useful forecast is built on actual cash timing, not accounting accruals:
- Opening cash for each week — your real bank position.
- Receipts — when customers will actually pay, based on their history and your terms, not the invoice date.
- Payments — wages, super, BAS and GST, rent, loan repayments, suppliers and tax, mapped to the week they leave the account.
- Closing cash for each week, which becomes the next week’s opening balance.
The output is a single line you can read at a glance: projected closing cash, week by week, with the dips visible weeks before they arrive.
Make it rolling, not static
A forecast built once and forgotten is worthless within a fortnight. The discipline is to roll it forward every week — drop the week just gone, add a new week 13, and update actuals against forecast. Over a month or two the variance between what you predicted and what happened tells you how reliable your assumptions are, and the model gets sharper.
The three mistakes owners make first time
- Forecasting from invoice dates, not payment dates. If a customer pays in 45 days, model 45 days — not your 14-day terms.
- Forgetting the lumpy outflows. Quarterly BAS, super, insurance and tax instalments wreck a forecast that only tracks weekly wages and suppliers.
- Building it once. The value is in the weekly roll-forward, not the first spreadsheet.
Where a virtual CFO adds value
Building the first model is the easy part. The value is in running it every week, reading what it’s telling you, and acting early — renegotiating terms, timing a purchase, drawing on a facility before you need it rather than after. That’s core virtual CFO work, and it’s often the first thing we put in place with a new client. See how we work.
Frequently asked questions
What is a 13-week cash flow forecast?
A rolling, week-by-week projection of cash in and out over the next quarter, based on actual payment timing. It shows your projected bank balance each week so you can act on shortfalls early.
How often should I update my cash flow forecast?
Weekly. Drop the week just past, add a new week 13, and compare actuals to forecast. A static forecast loses value almost immediately.
What’s the difference between a budget and a cash flow forecast?
A budget plans profit and performance over a year. A cash flow forecast tracks the actual timing of money in and out. You need both — they answer different questions.
Book a free 30-minute consultation and we’ll pressure-test your cash position and set up a forecast you can actually run.