Business Activity Statements (BAS)
Everything you need to know: from what a BAS is, to lodgement, mistakes, and why a registered BAS agent matters.
What Is a BAS?
A business activity statement (BAS) is the document you submit to the ATO declaring how much you earned for the period (whether that’s a quarter, a month, or another reporting frequency) and how much you spent on purchases.
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It also shows how much GST you collected on those earnings and how much GST you paid on those purchases. Those two amounts offset each other, and the difference is what you either pay to the ATO or receive as a refund.
In short: The BAS is the piece of paper. The GST (goods and services tax) is the actual tax. The BAS is simply how you report it.
Here’s how the GST calculation works at its simplest:
| Amount | GST Component (10%) | |
|---|---|---|
| GST collected on sales | $100,000 | $10,000 |
| GST paid on purchases | $40,000 | $4,000 |
| Net GST payable to ATO | $6,000 |
If your GST paid on purchases exceeds GST collected on sales, you receive a refund from the ATO instead.
What Is a Registered BAS Agent and Why Does It Matter?
If you prepare a BAS for a fee, you must be registered as a BAS agent. But beyond that legal requirement, a registered BAS agent can do things an unregistered bookkeeper simply cannot.
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The key distinction: a bookkeeper can process transactions, but only a registered BAS agent can determine whether GST applies to a transaction and how it should be recorded. That’s a significant difference when it comes to accuracy and compliance.
| Registered BAS Agent ✔ | Unregistered Bookkeeper ✘ |
|---|---|
| Lodge BAS, payroll, super & STP | Process transactions only |
| Advise on GST applicability | Cannot advise on GST |
| Advise on wine, luxury car & fuel tax | Cannot advise on indirect taxes |
| Bank transaction coding decisions | Can code, not decide |
| Taxable payments annual reporting | Limited compliance scope |
| Liaise with ATO on your behalf | Cannot represent you to the ATO |
| Seek penalty remission | Cannot seek remission |
| Request lodgement deferrals | Cannot request deferrals |
Businesses may still need an accountant for end-of-year tax, but a BAS agent can handle everything else.
BAS Due Dates
Normally, BAS is due on the 28th of the month following the end of the quarter or reporting period. But when you lodge through a registered BAS agent, you get an extra month’s extension on both lodgement and payment.
| Quarter | Standard Due Date | Via BAS Agent (Extended) |
|---|---|---|
| Q1 — July to September | 28 October | 25 November |
| Q2 — October to December | 28 February | 28 March |
| Q3 — January to March | 28 April | 26 May |
| Q4 — April to June | 28 July | 25 August |
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Important: The lodgement date and the payment date are the same. Many business owners lodge on time but forget to pay, and the ATO will charge interest on unpaid amounts. At the time of writing, the ATO interest rate is around 11%, and it goes up regularly. |
If you need even more time, a BAS agent can contact the ATO directly to request a further deferral. The ATO isn’t always willing, but having a registered agent liaise on your behalf can make a real difference, both in outcome and in avoiding a stressful conversation with the ATO yourself.
How Often Do You Need to Lodge BAS?
Your reporting frequency depends on your turnover, but you can also voluntarily register for a different frequency. Most businesses default to quarterly, every three months.
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Some business owners prefer monthly BAS. It means more regular (smaller) bills, which makes it easier to budget and set aside the GST component as you go. Quarterly reporting can catch businesses off guard if they’ve already spent the money they owe.
| Frequency | Who It Applies To | Key Benefit |
|---|---|---|
| Monthly | Higher-turnover businesses; or voluntary opt-in | Smaller, more predictable bills and easier cash flow management |
| Quarterly | Standard for most small businesses | Less admin; four lodgements per year |
| Annually | Very small businesses (ATO-determined) | Minimal reporting burden |
How Much Do You Pay?
GST is 10%. You collect 10% on your sales and pay 10% on your purchases. The BAS calculates the difference. If you’ve collected more than you’ve paid, you owe the ATO. If you’ve paid more in GST than you’ve collected, you get a refund.
The Key Sections of a BAS Form
The ATO has simplified the BAS form over the years. Here’s what the key labels mean:
| BAS Label | What It Is | Who Needs It |
|---|---|---|
| G1 | Total sales for the period (including GST-free sales) | All GST-registered businesses |
| 1A | GST collected on sales | All GST-registered businesses |
| 1B | GST paid on purchases (your credit) | All GST-registered businesses |
| W1 | Total wages paid to employees | Businesses with employees |
| W2 | PAYG tax withheld from wages | Businesses with employees |
| 5A | Income tax instalment (quarterly) | Businesses directed by ATO, usually after year 1 or 2 |
Label 5A is the one that tends to catch people off guard. After your first year of business, the ATO may require you to pay income tax in quarterly instalments alongside your BAS. You can choose to pay a set instalment amount, or calculate one based on your actual income for that quarter. It’s worth understanding before it appears on your form.
GST-Free Businesses: Do You Still Need BAS?
Yes, and often it works in your favour. Even if your business doesn’t charge GST (for example, some NDIS and medical businesses), you’re likely still spending money on purchases that include GST, things like office supplies, software, and equipment.
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By lodging a BAS, you can claim back the GST on those purchases. That means businesses that collect zero GST on sales can still receive a refund, in line with their regular lodgement schedule.
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Many GST-free businesses also have employees, so they still need to report PAYG withheld. Another reason to lodge regularly.
| GST-Charging Business | GST-Free Business (e.g. NDIS) | |
|---|---|---|
| GST on sales | $8,000 collected | $0 collected |
| GST on purchases | $2,000 paid | $1,500 paid |
| BAS outcome | Pay $6,000 to ATO | Receive $1,500 refund |
| PAYG withheld | Report if applicable | Report if applicable |
What Do Sole Traders Need to Know?
- If you're charging GST, you need to keep proper records of it.
- If you have employees, you must report their PAYG withholding on your BAS.
- After your first year of business, the ATO may require you to pay income tax instalments quarterly alongside your BAS. This can come as a surprise if you're not expecting it.
How to Lodge Your BAS
| Lodgement Method | Extended Due Date? | Best For |
|---|---|---|
| Registered BAS agent | Yes, extra month | Most businesses; least admin, most support |
| ATO Online Services for Business | No | Confident DIY lodgers |
| Paper statement | No | Rarely used; not recommended |
For most businesses, lodging through a BAS agent is the most practical choice. It removes the administrative burden, gives you more time, and means you have professional support if anything needs to be reviewed or corrected.
Penalties for Late Lodgement
The ATO will generally issue a fine of around $330 for a first late lodgement. Depending on how late it is, they may simply send a warning letter. But if late lodgement becomes a pattern, fines can reach around $800 per occurrence.
| Situation | Likely Outcome |
|---|---|
| First late lodgement | Warning letter; possible $330 fine |
| Repeated late lodgement | Fines up to ~$800 per occurrence |
| Seeking remission (natural disaster etc.) | May be granted; not guaranteed |
| Seeking remission for illness | Not always granted — ATO is firm |
| Via BAS agent with valid explanation | Better chance of a favourable outcome |
Key point: It’s very difficult to have these fines lifted. The ATO requires a compelling reason — such as a natural disaster. Even in cases of serious illness, remission isn’t guaranteed. Prevention is far easier than disputing a penalty after the fact.
If you do receive a penalty, speak to your BAS or tax agent about the circumstances. They may be able to seek remission on your behalf, and they can help you put systems in place to avoid it happening again.
What Happens If You Make a Mistake on a BAS?
Mistakes happen — especially when business owners are managing their own bookkeeping. The most common errors involve miscoding transactions (for example, recording a sale as a capital contribution rather than income), which can lead to under-reported GST.
How to fix it:
Your BAS agent can amend the lodged BAS, or depending on the size of the error, roll the adjustment into the next BAS period. For significant errors, amending the BAS directly is the right approach.
How serious is it?
It depends on the amount and the intent. If it's a genuine mistake and you're working with a BAS agent who can demonstrate that, the ATO is generally more lenient. But if there's any suggestion of deliberate avoidance, the ATO will take it seriously. This is one of the clearest reasons to work with a registered BAS agent: they can liaise with the ATO on your behalf, explain errors in context, and help navigate any follow-up so you don't have to face it alone.
Frequently Asked Questions
Do I have to register for GST and lodge a BAS?
You must register for GST (and therefore lodge a BAS) if your business turnover is $75,000 or more per year ($150,000 for non-profits). Below that threshold, registration is optional, but you may choose to register voluntarily.
What's the difference between lodging and paying? Aren't they the same deadline?
Yes, they are, and that’s exactly what confuses many business owners. The lodgement date and the payment date are the same. Lodging your BAS on time without paying means the ATO will still charge interest on the outstanding amount, currently around 11% per annum.
I'm GST-free. Do I really need to bother with a BAS?
Almost certainly yes. Even if you don’t charge GST on your sales, you’re likely paying GST on business purchases: office supplies, equipment, subscriptions. Lodging a BAS lets you claim that GST back as a refund. If you also have employees, you must report PAYG withheld regardless of your GST status.
Can I do my own BAS, or do I need an agent?
You can lodge your own BAS through the ATO’s Online Services for Business. However, you won’t get the extended lodgement and payment deadline that comes with using a registered BAS agent, and you take on full responsibility for accuracy. If your bookkeeping is complex, or you’re unsure about GST treatment on certain transactions, working with a registered agent is usually the safer option.
What if I genuinely can't pay my BAS on time? What are my options?
Contact the ATO (or have your BAS agent do it) as early as possible. The ATO may agree to a payment plan, which allows you to pay the debt in instalments. Acting proactively, before the deadline passes, puts you in a much better position than waiting for a debt to accumulate. A BAS agent can negotiate these arrangements on your behalf.
Need help with your BAS?
Working with a registered BAS agent takes the stress out of compliance, and often saves you money through accurate GST claims, extended due dates, and professional handling of anything the ATO throws your way.