GST and BAS timing: how your settings change your cash flow

Why is GST a cash flow problem at all?

GST isn’t your money. You collect it on the ATO’s behalf and hold it until the next BAS is due. Because it sits in your operating account for weeks or months, it’s easy to spend without noticing. And on the wrong settings, you can owe GST on sales your customers haven’t paid for yet.

Changing your settings won’t change how much GST you pay over a year. It changes when you pay it, and for a seasonal or slow-paid business, timing is everything.

Setting 1: How often do you report GST?

The ATO offers three reporting cycles:

Quarterly payers with GST turnover under $10 million may also be able to use the GST instalment method, paying an ATO-calculated amount each quarter and squaring up in an annual return.

Which suits a seasonal business? A Barossa cellar door or a Snowy Mountains lodge that takes most of its revenue in a few months can find a quarterly bill landing after the peak has already been spent. Monthly reporting keeps each payment close to the sales that created it. If you often get refunds — during a pre-season stock build or a fit-out — monthly reporting brings that cash back sooner.

Setting 2: Cash or accruals accounting?

The ATO lets businesses with aggregated turnover under $10 million choose cash accounting:

• Cash basis. You report GST in the BAS covering the period when you actually receive payment for sales or actually pay for purchases.
• Accruals (non-cash) basis. You report GST on a sale in the period you issue the tax invoice or receive any payment, whichever comes first — whether or not the customer has paid in full.

For a business with long debtor days, the difference is real. A builder with progress claims sitting unpaid for 30 or 45 days, or a consulting firm billing on 60-day terms, can owe GST on accruals before the money arrives. Cash accounting removes that gap on the sales side.

The trade-off: on a cash basis you also claim GST credits only when you pay suppliers. If you buy heavily on credit ahead of a season, accruals might bring those credits forward. Your accountant can model both.

Setting 3: When is each BAS actually due?

From the ATO’s BAS due dates:

Monthly BAS is generally due on the 21st of the following month. If a due date falls on a weekend or public holiday, you can lodge and pay on the next business day. Registered tax and BAS agents may have different dates for their clients.

Map these dates against your own year. For a Cairns tour operator, the 28 February payment covers the start of the wet season and lands in a quiet month. For a retailer, the same date covers Christmas trading — which should already be sitting in a GST account.

What about GST on imported stock?

Importers generally pay GST when goods are cleared at Port Botany, the Port of Melbourne, the Port of Brisbane or Fremantle — often months before the stock sells. You claim it back in your BAS, but in between it’s cash out of the business. The ATO’s deferred GST scheme lets approved importers defer that GST to their monthly BAS instead of paying at the border. For wholesalers, it’s worth asking about. See our working capital cycle guide for how import timing stretches your cash.

Habits that prevent a BAS squeeze

1. Run a separate tax account. Move the GST component of every receipt (one-eleventh of a GST-inclusive sale) across as it comes in.
2. Add PAYG withholding and instalments to the same account. They’re due on the same BAS.
3. Reconcile before each due date. Check the tax account against what the BAS will show.
4. Match your cycle to your season. Seasonal businesses often do better reporting monthly.
5. Don’t pay this quarter’s BAS from next quarter’s GST. It’s the most common way a small shortfall becomes a large one.
6. Talk to your accountant before switching — changing basis or cycle can have one-off effects.

What if a BAS lands at the wrong time?

It happens — a strong quarter’s GST falls due in a quiet month, or a major customer pays late.

• Lodge on time regardless. Failure-to-lodge penalties are separate from the debt itself.
• Contact the ATO before the due date. Payment plans are available, but interest keeps accruing, and the ATO’s general interest charge is no longer deductible from 1 July 2025.
• Use a short-term facility. A business line of credit can pay the BAS on the due date, then be repaid as customers settle their invoices. It’s generally for businesses trading six months or more.
• Clear accumulated ATO debt. If several quarters have built up, a property-secured top-up of $20,000 to $1m can refinance or pay out the ATO, secured on property you or a supporting party already own.

A quick settings check

PAYG instalments and super payments share the same calendar pressure — see PAYG instalments for seasonal businesses and Payday Super and cash flow.

If a BAS is coming up and the cash isn’t there yet, you can start a 60-second enquiry, or read how a facility helps with paying the ATO on time.

This guide is general information only — talk to your accountant about the right GST settings for your business.