Business Activity Statement (BAS)

The BAS is the quarterly or monthly form where GST-registered businesses report the GST they collected, claim GST credits, and settle PAYG withholding and instalments. Lodged through myGov or accounting software, it is due 28 days after each quarter, and spending the GST in the meantime is the classic trap.

Payslip & TaxLast reviewed 2026-09-27

What it is

The Business Activity Statement is the periodic tax report every GST-registered Australian business must lodge, usually quarterly. On one form you tell the ATO three things: how much GST you collected from customers, how much GST you paid on business purchases and can claim back as credits, and any PAYG amounts you owe, whether instalments on your own income or withholding from employees' wages. The net position becomes one bill or one refund.

For a sole trader the arithmetic is simple in theory. You collected 10% GST on your sales all quarter, you paid GST on your laptops and materials, and the difference belongs to the ATO. The BAS is where that reconciliation happens, due 28 days after each quarter ends, with a longer runway if you lodge through a registered tax agent.

The form's danger is psychological, not mathematical. GST collected sits in your bank account looking like revenue for up to four months. It was never your money. The BAS is simply the day the ATO comes to collect what you were holding in trust, and thousands of side businesses discover solvency problems exactly on that day each quarter.

Key takeaways

The BAS reports GST collected, GST credits claimed, and PAYG withholding or instalments in one periodic form.
Quarterly lodgement is due 28 days after each quarter ends; tax agents get you a longer extension.
GST you collect is never your money; it is the ATO's cash temporarily parked in your account.
Small businesses under $75,000 turnover need not register for GST and never lodge a BAS.
Lodging late attracts failure-to-lodge penalties on top of interest, even when the amount owing is small.

How it works

The quarterly cycle runs like this. All quarter you issue invoices with 10% GST added, and you keep tax invoices for business purchases over $82.50 because those are your credit evidence. When the quarter closes, your accounting software or myGov totals both sides.

Say you invoiced $22,000 plus $2,200 GST, and you bought $5,500 of materials carrying $500 of GST. Your BAS reports $2,200 collected, claims $500 of credits, and the net $1,700 is payable. If you employ anyone, their withheld PAYG appears on the same form, and if you are in PAYG instalments, that obligation appears too.

Lodgement is digital. Sole traders use the ATO's online services through myGov; most growing businesses lodge from Xero, MYOB or similar, which prefills the labels from the ledger. Payment is separate from lodgement: you can lodge and still need to transfer the cash by the due date. Refunds, when credits exceed collections, land in days and are one of the few fast things the system does.

The discipline the BAS forces is segregation. Smart operators move the GST slice of every invoice into a separate savings account on receipt, so BAS day is a transfer, not a crisis. Budget the set-aside with the budget planner or model take-home after GST with the freelancer pay calculator.

Why it matters

GST is the only tax that arrives in your account disguised as turnover. Every other tax is withheld or billed, but GST sits there for a quarter being indistinguishable from profit, which is why the ATO's most reliable small-business collection event is the BAS due date. Getting the segregation habit right is the difference between a business and a slow-motion debt spiral.

A colleague named Brent (yes, that Brent) ran a consultancy that collected $11,000 of GST across two quarters and treated it as working capital, meaning he spent it. The consolidated BAS demanded $7,400 net after credits on a Tuesday. He paid it off a personal credit card at 20% interest and described the ATO as unreasonable, a position the GST labels on his own invoices contradicted. The separate account exists precisely for people who trust their future selves too much.

The highest-leverage habits are boring: separate account for GST from invoice one, buy through the business so credits accumulate, and lodge through a tax agent if deadlines are your weakness, because their extension is real. If your side income is approaching $75,000, model the registration jump with the freelance rate calculator before the ATO models it for you.

Real-world examples

A quarter with $2,200 of GST collected

A tradie invoices $22,000 plus GST across the September quarter, collecting $2,200 of GST. He spends $5,500 on materials including $500 of GST, and holds every tax invoice. His BAS at 1A reports $2,200, at 1B claims $500, and he pays the $1,700 net by 28 October. Because he moved $200 of every $2,200 invoice into a GST account on payment day, the transfer is uneventful; the habit pairs well with the budget planner. His mate who did not segregate pays the same $1,700 from an overdraft.

A refund quarter after an equipment purchase

A photographer buys a $6,600 camera kit carrying $600 of GST in a quarter where she only invoiced $8,800 plus $880 of GST. Her BAS reports $880 collected and $600 in credits, a net payable of just $280; in her previous quiet quarter the credits actually exceeded collections and the ATO refunded $350 within a week. Big legitimate purchases in slow quarters flip the BAS from bill to refund, one of the system's few pleasant surprises. Keep the tax invoice, because no invoice means no credit.

Late lodgement on a small bill

A sole trader owes a modest $420 net GST for a quarter and forgets to lodge for two months. The failure-to-lodge penalty for a small entity runs one penalty unit per 28 days overdue, up to five units; at $313 per unit that quarter's two missed periods attract roughly $626 of penalty, exceeding the tax itself, plus general interest charge on the $420. Lodging on time with a payment plan for the balance would have cost zero in penalties. The form matters more than the money.

Common mistakes

Mistake: Treating collected GST as spendable revenue.

Why it bites you: It is the ATO's cash in your account. Brent spent $11,000 of it across two quarters and paid the BAS off a 20% credit card.

Mistake: Losing tax invoices and claiming credits anyway.

Why it bites you: Purchases over $82.50 need a valid tax invoice to support the credit. In an audit, unsupported credits are reversed with penalties and interest stacked on top.

Mistake: Thinking late lodgement is fine when the amount is small.

Why it bites you: Failure-to-lodge penalties apply to the form, not the bill. Two missed periods on a $420 BAS can cost roughly $626 in penalties alone.

Mistake: Registering for GST before the law requires it.

Why it bites you: Under $75,000 turnover registration is optional, and opting in means quarterly BAS forever, plus 10% added to your prices. For most side hustles it is admin without payoff.

Ivy's take

I spent an evening reading the BAS labels and the failure-to-lodge penalty schedule so you don't have to, and the system's personality is clear: friendly about refunds, vindictive about forms. Owe $420 and lodge eight weeks late and the penalty exceeds the tax. Owe nothing and lodge on time and everything is fine. The ATO is a paperwork absolutist.

The single habit that separates calm sole traders from panicked ones is the GST bucket account, and I will die on this small hill. Ten per cent of every invoice, moved the day it is paid, never touched, no exceptions for conference tickets. BAS day then becomes a $0 emotional event. Brent called his BAS bill unreasonable while unknowingly holding an invoice trail proving the money was never his. Do the segregation; the quarterly ritual stops being a ritual sacrifice.

Related jargon, defined

GST: The 10% goods and services tax businesses collect for the ATO on top of their prices.
Input tax credit: The GST paid on business purchases that you claim back at label 1B of the BAS.
Tax invoice: The document evidencing GST on a purchase, required for credits over $82.50.
Failure to lodge penalty: Penalty units charged per 28 days a BAS is late, regardless of the amount owed.
General interest charge: Daily-compounding ATO interest on unpaid balances, running above 10% per annum.
PAYG instalment: Prepayments toward your own income tax, reported on the same BAS when applicable.

Frequently asked questions

Who has to lodge a BAS in Australia?+

Any business registered for GST, which is compulsory once rolling turnover passes $75,000 ($150,000 for non-profits). You also get a BAS if you have PAYG withholding obligations as an employer, even with modest turnover.

When is the BAS due each quarter?+

Quarterly BAS is due 28 days after the quarter closes: 28 October, 28 February, 28 April and 28 July. Lodging through a registered tax agent typically buys you an extra month or more on most quarters.

What happens if I lodge my BAS late?+

Failure-to-lodge penalties apply per 28-day period overdue, charged in penalty units worth $313 each in recent years. The penalty applies to the form itself, so even a small bill can attract penalties bigger than the tax.

Can the ATO owe me money from a BAS?+

Yes. When your GST credits exceed the GST you collected, common after big equipment purchases or slow quarters, the BAS produces a refund. The ATO usually pays refunds within days of lodgement.

Do I need a BAS if I earn under $75,000?+

Not if you never registered for GST and have no employees. Voluntary registration is allowed but saddles you with quarterly lodgements, which is why most sub-threshold sole traders stay out of the system.

Disclaimer: This information is general in nature and does not constitute financial or legal advice. Always consult a qualified professional for your specific situation.

Keep learning

Australian Business Number (ABN)Pay As You Go Instalments PAYG Withholding Tax Deduction Tax Return

Business Activity Statement (BAS)