Quick answer
A 13-week cash flow forecast lists your opening bank balance, then week by week the cash you expect to receive and the cash you expect to pay, for the next quarter. Each week's closing balance becomes the next week's opening balance. Its job is to show your lowest point in advance, so you can move a payment, chase a debtor or arrange funding before the shortfall arrives.
Key points
- Thirteen weeks is one quarter — long enough to catch a BAS, short enough to estimate honestly.
- Forecast cash, not profit: record money when it hits or leaves the bank.
- The single most useful output is your lowest closing balance and the week it happens.
- Roll it forward weekly: drop the week just gone, add a new week 13.
A budget tells you what you hope the year looks like. A 13-week cash flow forecast tells you what next Thursday looks like. For most small businesses it’s the more useful document, and it takes less than an hour to build the first time.
What is a 13-week cash flow forecast?
It’s a week-by-week table of the cash you expect to receive and pay over the next quarter. Each column is a week. Each row is a type of receipt or payment. At the bottom you get a closing bank balance for every week.
Unlike a profit and loss statement, it ignores when a sale is earned and records only when money moves. That distinction is the whole point: you can be profitable on paper and still bounce a wage run because your biggest customer pays on 45-day terms.
What goes in the forecast?
Keep categories few and meaningful. A typical layout:
| Section | Rows | Where the numbers come from |
|---|---|---|
| Opening balance | Bank balance at start of week 1 | Your bank feed today |
| Cash in | Customer receipts, deposits, other income | Debtor ledger, bookings, sales history |
| Cash out — regular | Wages, super, rent, suppliers, loan repayments | Payroll, leases, supplier terms |
| Cash out — lumpy | BAS, PAYG instalments, insurance, registrations | ATO portal, renewal notices |
| Closing balance | Opening + in − out | Calculated |
Two rows deserve special care.
Super. From 1 July 2026, Payday Super applies: the ATO treats a contribution as on time when the fund receives it no later than 7 business days after payday (new employees get 20 business days). In practice super now leaves with every pay run, not in a quarterly lump, so put it in the same weeks as wages.
BAS. Quarterly lodgers pay on 28 October, 28 February, 28 April and 28 July; monthly lodgers pay by the 21st of the next month. Lodging online can add extra time for some quarters. Put the amount in the week you will actually pay it. Our small business tax calendar lists the dates for the year.
How do you estimate cash coming in?
This is where forecasts go wrong, usually by being optimistic. A few rules help:
- Start with invoices already issued. For each, estimate the week it will really be paid — based on that customer’s habits, not your terms.
- Add booked or contracted work in the week you expect to invoice, plus the customer’s usual payment delay.
- Then add “normal” trading from recent history — for example, the average of the last eight weeks of card takings for a café.
- Discount the uncertain. If a big payment might slip, put it a week or two later than you hope.
If you’re not sure how long customers take, pull a report of invoices paid in the last three months and look at the gap between issue date and payment date. That number is your real terms, whatever the invoice says.
How do you estimate cash going out?
Outgoings are easier because most are fixed or contractual. List wages and super by pay cycle, rent by due date, loan repayments by schedule, and supplier payments by the terms you actually use. Then scan the last twelve months of bank statements for the annual and quarterly items people forget: insurance premiums, vehicle registrations, software renewals, professional memberships, accountant’s fees.
Halfway through? If your early numbers already show a gap you can’t close with timing alone, it’s worth a quick conversation about funding options — enquiring won’t leave a mark on your credit file.
How do you read the result?
Look for three numbers:
- Lowest closing balance and the week it happens.
- Weeks below your comfort line — the minimum you want in the bank at any time.
- Direction of travel — is week 13 higher or lower than week 1?
A forecast that dips once and recovers suggests a timing gap. A forecast that trends down week after week points to a burn problem; see cash burn rate for how to measure and fix it.
Illustrative example. A physiotherapy clinic starts the quarter with $48,000 in the bank. Weekly receipts average $22,000 and regular outgoings $19,500. The forecast looks healthy until week 5, when a $31,000 quarterly BAS lands in the same week as a $9,000 insurance renewal. The closing balance drops to about $20,000 — below the owner’s $25,000 comfort line — before recovering by week 8. Knowing this in week 1 gives the owner a choice: split the insurance into instalments, chase two large health-fund receivables, or arrange a small standby facility.
How do you keep it up to date?
Once a week, replace last week’s estimates with what actually happened, delete the finished week and add a new week 13. Compare actual to forecast: if receipts keep falling short, your assumptions need adjusting, not just the numbers. It’s a 20-minute job and it’s the core of our weekly money routine.
If spreadsheets aren’t your thing, our 13-week cash-flow forecaster does the arithmetic, charts the balance and tells you your runway.
From forecast to funding
The best time to arrange finance is when the forecast shows a dip that is still six weeks away. Lenders — and you — have options then. At the last minute, you have fewer.
If your forecast shows a gap, tell us about it. We look at trading businesses for unsecured and cash-flow facilities typically from $5,000 to $500,000, and property-secured loans from $20,000 to $5,000,000. There’s no credit check when you first make contact, your enquiry isn’t shopped around to other lenders, and a real person who reads forecasts for a living will call you. Put your real numbers in the form — the more accurate they are, the more useful that first call becomes.
Frequently asked questions
Why 13 weeks rather than 12 months?
Thirteen weeks is a full quarter, so it always contains at least one BAS or PAYG cycle, plus several wage runs and rent payments. It's also short enough that you can estimate receipts from real invoices and bookings rather than guesses.
Should the forecast include GST?
Yes. A cash forecast tracks money in the bank, so receipts include the GST your customers pay and outgoings include GST you pay suppliers. The net amount then leaves when you pay your BAS.
What if my income is unpredictable?
Use conservative estimates and a range. Many owners forecast a realistic case and a slow case side by side. If the slow case still stays above your minimum balance, you're in good shape.
Can I use a spreadsheet instead of software?
Absolutely. A simple spreadsheet with weeks across the top and categories down the side works well. Our free online forecaster does the same job in a browser and lets you download the result as a CSV file.
What should I do if the forecast shows a shortfall?
First look at timing fixes: chase overdue invoices, move discretionary spending, ask a supplier for more time or bring forward a deposit. If a gap remains, that's the moment to talk about a funding facility — while you have weeks, not days, to arrange it.