The 13-week cash flow forecast: see trouble before it arrives

Most small businesses that run short of cash didn’t see it coming — not because the warning signs weren’t there, but because nobody was looking at the right number. The profit and loss says the business is fine. The bank balance looks fine today. And then three weeks from now, the BAS, a big supplier invoice and two pay runs land in the same fortnight as a customer paying late.

A 13-week cash flow forecast is the simplest tool for seeing that fortnight coming. It takes a couple of hours to set up and twenty minutes a week to maintain. This guide shows how to build one, what to put in it, and how to read it — including when it tells you that short-term finance would help, and when it tells you it wouldn’t.

What is a 13-week forecast, and why 13?

It’s a table with thirteen columns — one for each week of the coming quarter — and rows for every source of cash in and every payment out. You start with the bank balance today, add what comes in each week, subtract what goes out, and carry the closing balance forward.

Thirteen weeks is a quarter. That captures:

• a full BAS cycle;
• six or seven fortnightly pay runs;
• most customer payment terms, even slow ones;
• rent, insurance and other monthly or quarterly bills.

It’s long enough to see trouble coming and short enough to forecast with some confidence. business.gov.au provides a cash flow statement template and explains how forecasting helps identify seasonal trends and prevent shortfalls; the 13-week version simply works week by week rather than month by month.

How do you set it up?

Step 1: Opening balance. Use today’s actual balance across your business accounts. Not what the accounting software says — what the bank says.

Step 2: Cash in, by week. List every expected receipt:

• customer payments (by customer, for large ones);
• cash and card sales;
• refunds (GST, income tax, insurance);
• asset sales;
• loan drawdowns.

Step 3: Cash out, by week. List every expected payment:

• wages (net pay on each pay date);
• PAYG withholding (with the BAS or on its own schedule);
• super;
• suppliers;
• rent and outgoings;
• BAS / GST;
• loan repayments;
• insurance, subscriptions, vehicle costs;
• owner drawings.

Step 4: Closing balance. Opening + cash in − cash out. That becomes next week’s opening balance.

What timing rules matter most?

The forecast is only as good as its timing. Three items catch owners out.

Customer receipts. Forecast when customers actually pay, not when your invoice says they should. If a big customer’s terms are 30 days but they’ve paid in 50 to 60 for the past year, forecast 60. Your bank statements hold the evidence.

Super under Payday Super. The ATO confirms that for employee earnings paid from 1 July 2026, contributions are on time only if received by the employee’s fund within 7 business days after payday. If you used to pay super quarterly, it now leaves the account after every pay run. Put it in the forecast in the week after each payday.

BAS. The ATO lists quarterly BAS due dates of 28 October, 28 February, 28 April and 28 July, and monthly BAS on the 21st of the following month. If the due date falls on a weekend or public holiday, you have until the next business day. Lodging online may give eligible businesses extra time for some quarters, but not quarter 2. Put the payment in the week it will actually leave the account.

A simple template

Illustrative layout — use your own figures.

	Wk 1	Wk 2	Wk 3	Wk 4	…	Wk 13
Opening balance
Customer receipts
Card / cash sales
Other receipts
Total in
Net wages
Super (Payday Super)
Suppliers
Rent / outgoings
BAS / PAYG
Loan repayments
Other
Total out
Closing balance

Add a final row: safe minimum balance — the lowest balance you’re comfortable holding. For many businesses that’s roughly a pay run plus a week of suppliers.

How do you read it?

Look for three things.

1. The low point. Find the lowest closing balance in the thirteen weeks and the week it falls. That’s the single most useful number in the forecast.

2. How the low point compares with your safe minimum. If the lowest balance stays above it, you’re fine for the quarter. If it dips below — or below zero — you have a gap, and you know its size and timing.

3. What causes it. Is the dip a timing problem (a big bill before a big receipt) or a structural one (more going out than coming in, week after week)?

That third point decides what to do.

When does the forecast say finance would help?

A timing gap — a single dip caused by payments landing before receipts — is exactly what short-term finance is built for. The forecast tells you:

• how much you need (the depth of the dip plus a margin);
• when you need it (the week before the dip);
• when it can be repaid (the week the balance recovers);
• how it’s repaid (the receipts that cause the recovery).

That’s a complete exit plan, drawn straight from the forecast. Pages like waiting on a late payment and funding a new contract show how this works in common situations.

If your forecast shows a timing gap, see whether a short-term loan fits — enquiring doesn’t touch your credit file.

When does it say finance won’t help?

A structural gap — closing balances trending down every week, with no recovery in sight — is different. Borrowing would cover the shortfall for a while, then leave the business with the same problem plus a loan to repay. The forecast is telling you to change something: prices, costs, payment terms, stock levels or the business model.

A recurring gap — dips that come and go every month — usually suits a line of credit better than a series of short-term loans. See short-term loan vs line of credit.

Be honest with yourself here. A forecast that’s been nudged to look better than reality is worse than no forecast at all.

How do you keep it accurate?

• Update weekly. Roll forward one week; add a new week 13.
• Replace forecasts with actuals for the week just gone, and note big differences.
• Learn from the differences. If receipts are consistently later than forecast, adjust your timing assumptions.
• Keep it simple. Thirteen columns and twenty rows is enough. Complexity makes it less likely you’ll maintain it.

After a month or two, the forecast becomes remarkably reliable — and remarkably calming.

How does a lender use it?

For short-term loans repaid from trading or a specific receipt, a clear forecast shows a lender that you understand your cash flow, that the loan is sized properly, and that the exit is credible. business.gov.au lists cash flow statements and financial forecasts among the documents to prepare when applying for a business loan. A realistic forecast — including the uncomfortable weeks — is more convincing than an optimistic one.

The exit strategy builder complements the forecast by turning your repayment date into a checklist of actions.

Illustrative: reading a real low point

Illustrative figures only. A plumbing business opens week 1 with $62,000. Weeks 1 to 4 look comfortable. In week 5 the quarterly BAS ($34,000) and a large supplier account ($28,000) both fall due, while the biggest customer’s payment ($71,000) isn’t expected until week 8. The closing balance in week 6 drops to –$9,000 against a safe minimum of $25,000.

The forecast has done its job: it shows a $34,000 shortfall to the safe minimum, landing in five weeks, caused by timing and fixed by a known receipt in week 8. That’s a clear case for a short, well-sized bridge — or for negotiating the supplier’s due date — and there are five weeks to arrange either calmly.

Put your forecast to work

If your 13-week forecast shows a gap with a clear recovery, tell us about it — the size, the timing and what brings the balance back up. A lending specialist will look at whether a short-term loan fits and how long it should run. Enquiring won’t show on your credit file, and your forecast and details stay with the person helping you. Please share the figures as they really are; an honest forecast gets you a loan that actually solves the gap.