Cash flow forecasting for a small business is the weekly habit of writing down what you expect to come in, what you know has to go out, and where the balance lands. It takes about an hour a week on a thirteen-week horizon. Done consistently it turns cash from something you react to into something you can see coming, which is the whole point.
Most small businesses do not fail the forecast because the maths is hard. They fail it because it is a project rather than a routine: built once in a spreadsheet, admired, and never opened again. The version that works is small enough to maintain.
Why thirteen weeks
A thirteen-week forecast covers a full quarter, which is long enough to catch a BAS instalment, a quarterly rent or insurance payment, and a seasonal swing, but short enough that the numbers are mostly known rather than guessed. Beyond a quarter you are forecasting the business; inside a quarter you are forecasting the bank account, and only the second one is reliable enough to act on.
Weekly buckets matter more than the horizon. A monthly forecast hides the problem where wages fall on the Thursday and the big receipt lands on the following Tuesday. The whole value of the exercise is in that level of detail.
The hour, step by step
Start with the actual bank balance. Not the accounting cash position, not the balance minus what you have mentally allocated. The number on the statement this morning. Everything else builds from there.
Pull the debtors ledger and put each invoice in the week you genuinely expect it to be paid, not the week it is due. If a customer has paid at sixty days for the last four invoices, they will pay at sixty days on this one. Forecasting against terms rather than behaviour is the single biggest source of optimistic forecasts.
Pull the creditors ledger and do the same in reverse, then add the payments that never appear on it: wages and superannuation, the ATO instalment, rent, insurance, loan and lease repayments, subscriptions, and the quarterly bills that arrive on a cycle you have stopped noticing.
Add expected new sales week by week, conservatively. This is the only genuinely uncertain line in the model, which is an argument for keeping it small and separate rather than blending it into the debtor figures.
Then read the bottom line across thirteen columns and look for the lowest point. That number, and the week it falls in, is the output of the whole exercise.
What to do with the low point
The low point tells you two things: how much headroom you need, and when you need it. Both are the questions a lender will ask, and having the answer already is the difference between a facility sized properly and one sized by guesswork.
If the low point is comfortably positive every week, you do not need a facility, and no one should be selling you one. If it dips below zero in a predictable, recurring pattern, an overdraft is usually the right shape. If it dips once because of a specific event, a term facility matched to that event is cleaner and cheaper.
If the dip exists only because customers pay slowly rather than because the business is short of capital, the problem is debtor timing rather than working capital, and what is invoice finance describes the structurally correct fix. Business overdraft vs unsecured business loan covers the choice when the gap really is general.
The forecast a lender wants to see
The weekly routine described here is for running the business. When you go to a lender the emphasis shifts: they want to see the peak funding need, whether the pattern is repeating, and how the facility gets repaid. That is a slightly different document, and cashflow forecasting for small business loans covers what it needs to contain.
The good news is that the second document falls out of the first almost for free. A business that has been maintaining a rolling thirteen-week forecast for six months can produce a credible funding case in an afternoon. A business starting from scratch the week it needs money cannot, and lenders can tell the difference.
Making it stick
Do it on the same morning every week, before the week starts. Monday before opening works for most businesses; Friday afternoon does not, because the temptation is to skip it when the week has been hard.
Keep the actual against the forecast. After a few weeks you will find your own bias, and it is almost always the same one: receipts land later than expected and costs arrive earlier. Once you know the size of your bias you can correct for it.
Resist adding detail. The forecast that survives is the one that takes an hour. Every extra line item is a reason to skip a week, and a forecast that is two weeks stale is worse than no forecast, because it is still believed.
Where to from here
Once the forecast shows you the shape of the gap, we compare working capital facilities across our whole lender panel and size the facility against the number rather than against a round figure someone picked. There are no fees to clients; the lender pays us when the finance settles. Book a 20-minute brief and bring the forecast with you, even a rough one.
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