Cash Flow Forecast for Australian Small Business: a 13-Week Example with GST, BAS and Super

A cash flow forecast is a week-by-week or month-by-month estimate of the cash coming into and going out of your business, so you can see a shortfall before it happens. For an Australian small business, the forecast has to include the money that isn't yours: GST (one-eleventh of every GST-inclusive receipt), PAYG instalments and withholding paid with your BAS, and super, which since 1 July 2026 is due with every pay run. A 13-week forecast, updated every Monday, is enough for most sole traders and small businesses.

What is cash flow?

Cash flow is the movement of money in and out of your bank account over a period. Positive cash flow means more came in than went out; negative means the opposite. It's about timing, not just totals: you can win $50,000 of work this month and still be unable to pay rent if the customers pay in 60 days.

Cash flow vs profit

Profit is income minus expenses, counted when the work is earned and the costs are incurred. Cash flow counts when money actually moves. A job invoiced in June is profit in June, but if it's paid in August, the cash arrives in August. GST makes the gap wider: the $1,000 of GST inside an $11,000 receipt sits in your account, but it belongs to the ATO and leaves again at BAS time.

What is a cash flow forecast?

A cash flow forecast projects your opening bank balance forward, adding expected receipts and subtracting expected payments for each week or month, to show your closing balance in each period. Its job is to show the lowest point before you reach it, so you can chase invoices, delay a purchase or arrange finance in time.

Two horizons cover most needs. A 13-week (one quarter) forecast, in weeks, is the working tool, because it catches the BAS payment, the Christmas slowdown and the gap between payday and customer payments. A 12-month forecast, in months, is for planning: hiring, buying a vehicle, or showing a lender.

What is the difference between a revenue forecast and a cash flow forecast?

A revenue forecast estimates the work you'll invoice in each period; a cash flow forecast estimates when that money will reach your bank. You need the first to build the second. Revenue forecasting usually starts from three sources: repeat customers and retainers you can count on, quotes you've sent multiplied by how often you usually win them, and last year's figures for the same months.

To turn revenue into cash, shift each month's invoices forward by how long customers really take to pay. If your days sales outstanding is 30, revenue you invoice in November mostly turns into cash in December. Use real payment behaviour, not your terms: if your invoices say 14 days but your aged receivables report shows customers paying in 35, forecast 35.

How do you build a cash flow forecast?

Start with today's bank balance, list every receipt you expect by the week it will arrive, list every payment by the week it will leave, and roll the closing balance into the next week. Here's the order that keeps it accurate:

1. Opening balance. Your actual business bank balance today, not what you think it should be.
2. Receipts from invoices already sent. Go through your unpaid invoices and put each one in the week you realistically expect payment. Leave very old debts out until they're paid.
3. Receipts from new work. Booked jobs and recurring invoices first, then a cautious estimate of new sales, shifted by your typical payment delay.
4. Regular payments. Wages, super, rent, loan repayments, vehicle, phone, software, insurance, and your own drawings.
5. Irregular and annual payments. Insurance renewals, registrations, licences, equipment, and BAS. These are the ones that cause surprises.
6. Closing balance. Opening + receipts − payments. That becomes next week's opening balance.

How do you include GST, BAS, PAYG and super in a cash flow forecast?

Treat them as separate lines with their own due dates. GST you collect is one-eleventh of each GST-inclusive receipt; it leaves your account when you pay your BAS. PAYG instalments and any PAYG withheld from wages are paid on the same BAS. Super now leaves with each pay run.

GST: one-eleventh of what you collect

If you're registered for GST, the GST inside a receipt is the total divided by 11: a $6,600 payment contains $600 of GST. Subtract the GST credits on your business purchases (also one-eleventh of each GST-inclusive bill) and the difference is roughly what you'll owe on your BAS. On the cash basis, you count GST when the money moves; on the accruals basis, you count it when you issue the invoice, so you may owe GST on sales you haven't been paid for yet. The ATO explains both on its page about choosing a GST accounting method. The GST calculator pulls GST out of any total.

BAS due dates for quarterly lodgers

These are the standard dates on the ATO's BAS due dates page. If you lodge online you may be eligible for an extra two weeks, and registered tax or BAS agents may get longer, but Q2 doesn't get the extra time because it already includes a one-month extension. If a due date falls on a weekend or public holiday, you have until the next business day: 28 February 2027 is a Sunday, so the Q2 BAS for 2026–27 can be paid on Monday 1 March. Monthly lodgers pay by the 21st of the following month. In your forecast, put the BAS payment in the week it's due, not the week you lodge.

PAYG instalments and PAYG withholding

If the ATO has put you into PAYG instalments, your quarterly instalment is paid on the same BAS, using the amount or rate on your instalment notice. If you employ staff, the tax you withhold from their wages is also paid through your activity statement. Both are money you're holding for the ATO, so forecast them alongside GST.

Super: now due with every pay run

Since 1 July 2026, under Payday Super, employers must pay super guarantee for each payday, and the contribution must reach the employee's fund within 7 business days (longer for a new employee's first contribution). The rate is 12% of qualifying earnings. For your forecast, that means super is no longer a quarterly lump; it's a line next to wages every pay cycle. The ATO's Payday Super page has the detail.

What does a 13-week cash flow forecast look like?

Here's a worked example for a GST-registered sole-trader electrician with one employee, on the cash basis, starting Monday 26 October 2026 with $8,000 in the bank. Receipts include GST. The employee is paid fortnightly: $1,300 net from $1,600 gross, plus $192 super (12%) paid the same week. The $300 of PAYG withheld each pay goes to the next BAS.

What the forecast shows:

• Week 1 is the low point. The Q1 BAS of $6,100 (GST of $4,300, PAYG withheld of $900 and a PAYG instalment of $900) is due Wednesday 28 October, the same week as a pay run, and cash drops to $3,198. Lodging online might push the due date out two weeks, but the money was always the ATO's.
• The first four weeks lean on old invoices. $14,300 of receipts come from invoices already sent. If those customers pay two weeks late, the account is overdrawn in week 1. Chasing them is the single most valuable job this month.
• Week 8 carries an annual bill. The $2,400 insurance renewal is why overheads jump to $3,060.
• Christmas costs about $7,600. Cash falls from $16,952 to $9,358 between weeks 8 and 11, because drawings and fixed costs continue while receipts stop.
• The closing balance isn't all yours. GST in receipts for weeks 1 to 9 (all in October–December) is about $5,100, less about $1,280 of GST credits on materials, plus $1,500 PAYG withheld from five pays and the next PAYG instalment. Roughly $6,200 of the $11,246 at the end belongs to the Q2 BAS due 1 March 2027.

Is there a free cash flow forecast template for Australian businesses?

Yes. business.gov.au has a free Excel cash flow statement template you can use for actual or forecast figures; download it from its page on how to set up a cash flow statement. It's built in months, so for a 13-week view, copy this layout into a spreadsheet with one column per week:

How can a small business improve cash flow?

Get paid sooner, pay out on time rather than early, and keep the tax money separate. The biggest gains for most small businesses come from the first, because it's the part most fully in your control.

• Shorten your terms. Net 7 or Net 14 instead of Net 30 brings receipts weeks forward. Our guide to invoice payment terms in Australia has wording to copy.
• Take deposits. For larger jobs, a deposit covers materials before you buy them. See how to issue a deposit invoice.
• Invoice the same day. Every day between finishing a job and sending the invoice is a day added to the wait.
• Make it easy to pay. BSB and account number, PayID and, where it suits, a card payment link. Our guide to accepting online payments compares the options.
• Chase on a schedule. A reminder the day after the due date, then at 7 and 14 days overdue. Our guide on chasing overdue invoices has the scripts. If you bill the same customers regularly, InvoiceSonic prepares recurring invoices for you to review and sends automatic reminders at 7, 14 and 30 days after the due date.
• Park the tax. Move one-eleventh of every GST-inclusive receipt, plus a share for PAYG, into a separate account each week, so the BAS never comes out of your operating money.
• Plan the quiet weeks. If your forecast shows a dip at Christmas or in a wet month, bring invoices forward, pull back drawings or delay a purchase before you get there.

A healthy forecast and healthy working capital go together: the faster your receivables turn into cash, the less buffer you need.

How often should you update a cash flow forecast?

Weekly for a 13-week forecast, ideally the same morning each week. Replace last week's estimates with what actually happened, roll a new week onto the end, and check the lowest balance in the next 13 weeks. If the lowest point is below what you need to operate comfortably, act now.

The common mistakes are predictable: forecasting receipts from invoice dates instead of real payment dates, forgetting the BAS, leaving out annual bills, treating GST in the bank as spending money, and being optimistic about new sales. Be conservative on receipts and generous on payments, and the forecast will rarely surprise you in a bad way.

This article is general information, not legal, tax or financial advice. For guidance specific to your situation, see business.gov.au and the ATO, or speak to a registered tax agent or BAS agent.

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