To lodge BAS correctly, you need to prepare accurate data, complete the right fields (G1, 1A, 1B, W1/W2), and review everything before submitting, the form itself is only the final step
BAS can be lodged online, via software, or through an agent, but your method should match how well your records are maintained and how complex your reporting is
A correct BAS lodgement doesn’t end at submission, you also need to pay on time, keep records, and ensure your figures can be backed if the ATO reviews them
Understanding how to lodge BAS correctly isn’t just about filling out a form, it’s about reporting your GST, PAYG, and business activity accurately to the ATO. Get it wrong, and you could face delays, penalties, or cash flow issues.
If you’re preparing for your next BAS lodgement, the process itself is straightforward but only if you have the right information ready and understand what each section requires.
In this guide, we’ll walk you through:
- How to lodge BAS
- Who needs to lodge BAS
- What you need before you start
- Common mistakes to avoid while lodging
By the end, you’ll also have a clearer sense of whether it makes more sense to lodge it yourself or work with a tax accountant.
For a cleaner BAS lodgement process, prepare your numbers directly from reconciled reports (GST, sales, payroll) instead of calculating them manually, this reduces errors and speeds up submission.
Who needs to lodge a Business Activity Statement (BAS) in Australia?
You need to lodge a Business Activity Statement (BAS) if your business has ATO reporting obligations such as GST, PAYG withholding, or PAYG instalments.
This typically applies if your business:
- Is registered for GST
- Pays employees and withholds PAYG tax
- Pays PAYG instalments towards income tax
- Claims fuel tax credits or other adjustments
Your Business Activity Statement (BAS) will only include the sections relevant to your business, you don’t need to complete every field.
What do you need before lodging BAS?
To lodge BAS correctly, you need accurate financial records covering your sales, expenses, GST, and payroll for the reporting period.
Before you start your BAS lodgement, make sure you have the following information ready:
- Sales invoices and total sales figures (G1)
This includes all income for the period, not just GST-inclusive sales. - Purchase and expense records (G10, G11)
Ensure all business expenses are recorded accurately, including GST paid on purchases. - GST collected and GST paid
You’ll need to calculate the GST on sales and the GST credits you can claim. - Wage and payroll records (W1, W2)
Include total wages paid and PAYG withholding amounts for employees. - PAYG instalment amounts (if applicable)
Based on your ATO instalment rate or previous BAS. - Fuel tax credits or other adjustments (if applicable)
Only relevant for businesses eligible to claim these credits. - Previous BAS or ATO notices (if required)
Useful for cross-checking instalments, adjustments, or carry-forward amounts.
Having this information prepared before you lodge BAS online will make the process faster and reduce the risk of errors.
What does each section of a BAS form mean?
Each section of your BAS form represents a specific part of your business activity, including sales, expenses, GST, and PAYG obligations and needs to be completed accurately to ensure correct reporting.
BAS field | What it means | What to include |
G1: Total sales | This is the starting point, your total business income for the period. | Include all sales (GST-inclusive and GST-free), not just taxable income. |
G2: Export sales | Income from sales made outside Australia | Only include export income if this applies to your business |
G3: Other GST-free sales | Sales where GST doesn’t apply | For example, basic food, exports, or certain GST-free services |
G10: Capital purchases | Larger, one-off business purchases or investments | Equipment, vehicles, or other business assets |
G11: Non-capital purchases | Your regular operating expenses | Rent, utilities, subscriptions, and day-to-day costs |
1A: GST on sales | The GST you’ve collected from customers | Based on your taxable sales during the period |
1B: GST on purchases | The GST credits you can claim back | GST paid on eligible business expenses |
W1: Total salary and wages | Total wages paid to employees before tax | Gross wages paid during the period |
W2: Amount withheld | Tax withheld from employee wages | PAYG withholding amounts |
W4/W5: PAYG instalment | Your income tax instalment for the period | Based on ATO rate or your calculated amount |
T1–T4: Tax calculation | Final step to work out your tax position | Used to calculate how much tax is payable |
Missing BAS due dates doesn’t just lead to penalties, it can also result in interest charges, increased ATO scrutiny, and potential compliance flags if delays happen repeatedly.
What are the different ways to lodge BAS in Australia?
When it’s time for your BAS lodgement, you have a few options but in practice, most businesses either lodge BAS online or use a registered BAS agent.
The right method depends on how your records are managed and how involved you want to be in the process.
Method | Best for | How it works | Key considerations |
Online Services for Business | Companies, trusts, partnerships | Log in via myGovID → Activity Statements → enter figures → submit | Most commonly used; secure and gives full visibility of past BAS lodgements |
myGov (ATO online services) | Sole traders | Log in to myGov → ATO → Activity Statements → complete and lodge BAS | Simple and mobile-friendly; only available for individuals |
SBR-enabled accounting software | Businesses using Xero, MYOB, QuickBooks | Prepare BAS in software → lodge directly via SBR | Fastest option if books are up to date; avoids re-entering data |
Businesses that want accuracy and support | Agent prepares and lodges BAS on your behalf | May provide extended deadlines; reduces errors and admin | |
Phone (nil BAS only) | Businesses with no activity | Lodge via ATO phone service | Limited use, only for nil BAS |
Paper form (mail) | Legacy or limited-access users | Complete and send BAS manually | Slow and prone to errors; rarely used today |
For most businesses, lodging BAS online is the standard approach, while using an agent becomes more common as complexity increases.
How to lodge BAS online with the ATO (step-by-step)
To lodge BAS online, you need to access your BAS through the ATO system, enter your figures accurately, review them, and submit the statement before the due date.
Step 1: Log in to the ATO system
Access your BAS through:
- Online Services for Business (for companies, trusts, partnerships)
- myGov (linked to ATO) for sole traders
- or your accounting software if it supports BAS lodgement
If your bookkeeping is up to date, software-based lodgement is usually the fastest option.
Step 2: Open your BAS for the correct period
- Navigate to Activity Statements
- Select the BAS for the relevant reporting period
Your BAS is already generated by the ATO, you’re reviewing and completing it.
Always confirm the reporting period before entering any figures.
Step 3: Enter your BAS figures
Using your prepared records, complete the relevant fields:
- G1, G10, G11: sales and purchases
- 1A, 1B: GST collected and GST credits
- W1, W2, W4/W5: PAYG amounts (if applicable)
Only complete the sections that apply to your business. Incorrect classification (e.g. GST-free vs taxable) is one of the most common BAS errors.
Step 4: Review your BAS carefully
Before lodging:
- Check GST amounts align with your records
- Confirm PAYG figures match payroll reports
- Review the final payable or refundable amount
If the numbers don’t look right, stop and review, this step prevents most issues.
Step 5: Submit your BAS
- Complete the declaration
- Lodge your BAS online
- Save your confirmation receipt
Online BAS lodgement gives immediate confirmation and reduces processing delays.
Step 6: Keep records and prepare for payment
After lodging:
- Save your BAS and confirmation
- Note the amount payable or refundable
- Prepare for payment by the due date
If you’re expecting a refund, online lodgement typically results in processing within 12–14 business days.
Should you lodge BAS yourself or use a BAS agent?
Whether you should lodge BAS yourself or use a BAS agent depends on how confident you are with your records and how complex your reporting is.
- If your bookkeeping is simple and up to date, lodging BAS yourself online is usually manageable
- If your BAS includes multiple components or you want to reduce risk, working with a BAS agent is often the better option
Many businesses start by lodging BAS themselves and move to an agent as their operations grow or become more complex.
How do you pay BAS or claim a refund from the ATO?
Once your BAS lodgement is complete, you’ll either need to pay the amount owed or receive a refund.
If you need to pay BAS
If your BAS shows a payable amount, payment must be made by the due date to avoid interest or penalties.
You can pay via:
- BPAY using your Payment Reference Number (PRN)
- Direct debit through ATO Online Services
- Credit or debit card
- Australia Post (less commonly used)
Always confirm your PRN before paying to ensure the payment is matched correctly.
If you’re expecting a refund
If your GST credits exceed GST collected:
- The ATO will process your refund after lodgement
- Online BAS lodgement typically results in refunds within 12–14 business days
- Refunds are paid directly to your nominated account
Delays usually occur if your BAS contains errors or requires review.
Lodgement vs payment
Lodging your BAS and paying your BAS are separate obligations:
- You can lodge on time but still incur penalties if payment is late
- Always check both lodgement due date and payment due date
What are BAS due dates and lodgement cycles in Australia?
BAS due dates depend on your lodgement cycle; monthly, quarterly, or annually, with most businesses lodging quarterly within 28 days after the end of each period.
Quarterly vs monthly lodgement
Your BAS lodgement frequency depends on your business size and GST turnover:
- Quarterly lodgers: most small to medium businesses lodge BAS every quarter, reporting GST, PAYG, and other obligations.
- Monthly lodgers: typically larger businesses or those with higher GST turnover lodge BAS monthly to keep reporting more consistent.
Your lodgement cycle affects your deadlines, cash flow planning, and compliance requirements.
Key BAS due dates (quarterly lodgers)
For most businesses lodging quarterly, BAS is due 28 days after the end of each quarter:
Quarter | Reporting period | BAS due date |
Q1 | July – September | 28 October |
Q2 | October – December | 28 February |
Q3 | January – March | 28 April |
Q4 | April – June | 28 July |
Monthly BAS is generally due 21 days after the end of each month.
Penalties for late lodgement
If you miss your BAS deadline, the ATO may apply penalties and interest, depending on how late the lodgement or payment is.
This can include:
- Failure to lodge (FTL) penalties: applied when your BAS is not lodged on time, with penalties increasing the longer the delay
- General interest charges (GIC): applied to any unpaid amounts until the balance is cleared
Even if you lodge your BAS on time, late payment can still result in interest charges.
In some cases, the ATO may remit penalties, but this is not guaranteed and depends on your compliance history.
What are the most common BAS lodgement mistakes to avoid?
Even when you lodge BAS online, errors can still occur. Most issues come from timing, incorrect figures, or incomplete records. Being aware of these helps you avoid penalties and unnecessary rework.
- Late lodgement or payment: Missing your BAS due date can result in penalties and interest charges. Set up calendar reminders or use accounting software alerts to ensure you lodge and pay on time.
- Incorrect GST reporting: Overstating or understating GST can create discrepancies with the ATO. Always reconcile GST on sales (1A) and GST credits (1B) against your invoices before lodging.
- PAYG withholding errors: Incorrect PAYG figures can lead to compliance issues. Cross-check W1 and W2 amounts with your payroll reports to ensure accuracy.
- Not saving confirmation receipts: After lodging your BAS online, you’ll receive a confirmation. Always save this as proof of lodgement in case the ATO requests it.
- Using outdated or incomplete records: Working with old or incomplete financial data often leads to incorrect BAS figures. Keep your bookkeeping up to date, ideally using cloud-based systems.
Avoiding these mistakes helps ensure your BAS lodgement is accurate, on time, and compliant.
If your payable amount seems higher or lower than expected, it’s worth reviewing your BAS before making payment, errors at this stage can impact both your cash flow and compliance.
Why is record-keeping important for BAS lodgement?
Record-keeping is critical for BAS lodgement because your GST, PAYG, and reporting figures are only as accurate as the data behind them.
Strong record-keeping helps you:
- Report GST accurately: correctly calculate GST on sales (1A) and GST credits (1B) without guesswork
- Avoid classification errors: clearly separate GST-free, taxable, and input-taxed transactions
- Keep PAYG figures aligned: ensure W1 and W2 match your payroll reports
- Reconcile before lodging: quickly verify your BAS totals before submission
- Handle ATO queries confidently: have supporting records ready if your BAS is reviewed
In practice, most BAS errors don’t come from the form, they come from incomplete or inconsistent records.
Keeping your books updated throughout the period, ideally using cloud accounting software, makes BAS lodgement faster, more accurate, and far easier to manage.
Read more: Best Accounting Platforms in Australia for 2026
Need help with BAS lodgement? Here’s how Sleek can support you
If you want to avoid errors, save time, and ensure your Business Activity Statement is lodged correctly, working with a registered BAS agent can make the process significantly easier.
Sleek’s registered BAS and tax agents help you manage the entire process with confidence:
- End-to-end BAS lodgement support: from preparing your BAS to reviewing figures and lodging directly with the ATO
- Handled by registered BAS agents: ensure your GST, PAYG, and reporting meet current ATO requirements
- Ongoing compliance: stay on top of lodgement cycles and avoid missed deadlines or penalties
- All-in-one support: accounting, bookkeeping, tax, and compliance managed together so your BAS is always based on accurate data
- Transparent, fixed pricing: clear pricing with no hidden fees, so you know exactly what to expect
For many businesses, BAS becomes less about submission and more about getting the numbers right. Having a professional handle it, ensures your lodgement is accurate, on time, and fully compliant.
Speak to a Sleek expert and get your BAS lodged correctly, without the back and forth.
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Frequently Asked Questions
Can I lodge a nil BAS online?
Yes, you can lodge a nil BAS online through the ATO portal or via phone (if eligible). This applies when you have no GST, PAYG, or other activity to report.
What is the difference between BAS lodgement and BAS payment?
BAS lodgement is submitting your statement to the ATO, while BAS payment is paying the amount owed. These are separate, you can lodge on time but still incur penalties if payment is late.
Can I revise a BAS after lodging it?
Yes, you can revise a BAS if you’ve made an error. This can be done through ATO Online Services or your accounting software, depending on how you originally lodged it.
