Most small businesses run on a bank balance and a feeling. The bank balance tells you where you have been. The feeling is usually wrong in one direction or the other, and it is always wrong at the worst time.
A 13 week cash flow forecast fixes this. It is the single most useful management report a small business can have, and it takes about two hours to build and twenty minutes a week to maintain.
Why 13 weeks
Long enough to see a problem coming while you can still do something about it. Short enough that you can forecast with reasonable accuracy, because you generally know who owes you money and what you owe over a quarter.
Anything beyond about 13 weeks becomes guesswork dressed up as a spreadsheet. Anything shorter does not give you time to act.
How to build it
Thirteen columns, one per week. Rows in three blocks.
Opening cash. What is actually in the bank at the start of the week. Not your accounting system's cash figure if it includes unpresented items. The real number.
Money in. By source, not in one lump. Customer receipts from existing debtors, week by week based on when they actually pay rather than when the terms say they should. New sales receipts. GST refunds. Anything else.
Money out. Wages, and now super with them since payday super started on 1 July 2026. Rent. Suppliers, by when the invoice falls due. Loan repayments. BAS and PAYG instalments on their actual due dates. Tax. Insurance and the annual bills that only appear once a year and always at the wrong moment.
Closing cash, which becomes next week's opening.
The three rules that make it work
Use payment behaviour, not payment terms. If a customer is on 30 days and reliably pays at 52, forecast 52. The forecast is a prediction, not a negotiation position.
Put the annual and quarterly items in. Insurance renewals, BAS, the annual software subscription, workers compensation, land tax, the accountant's fee. These are the things that turn a comfortable week into an overdraft, and they are entirely predictable.
Update it weekly, at the same time. Friday morning works for most people. Roll the window forward one week, replace last week's forecast with what actually happened, and look at where the forecast was wrong. After a month you will know your own business's patterns better than any report has ever told you.
What to look for
The lowest point, not the ending balance. A forecast that ends at $80,000 but dips to negative $12,000 in week seven is a forecast of a problem.
The gap between the forecast and the actual, week by week. If you are consistently optimistic on receipts by 15 per cent, that is information about your debtors and about yourself.
Any week where a single large receipt is doing all the work. That is concentration risk and it is worth having a plan for.
Why this matters more this year
Two changes have removed slack that a lot of businesses were quietly relying on.
Payday super means superannuation now leaves the business with every pay run rather than quarterly. The amount has not changed. The timing has, and for a business that was using the quarterly gap as a buffer, that buffer is gone.
And ATO interest is no longer deductible, so falling behind on tax is a more expensive way to fund working capital than it used to be. It was never a good one.
A forecast will not create cash. It will tell you three weeks earlier that you are going to need some, which is the difference between arranging finance and begging for it.