Unsure how to lodge your BAS correctly?
Running a business in Australia means dealing with more than just sales and customers, you also need to stay on top of tax reporting. One of the biggest obligations for GST-registered businesses is the Business Activity Statement (BAS), a form that reports your GST, PAYG, and other tax liabilities to the Australian Taxation Office (ATO).
If you’ve ever wondered what BAS is, how to lodge it, or when it’s due, this guide will walk you through everything step by step. You’ll learn how BAS works, who needs to lodge it, the different lodgement methods, and how to avoid common BAS mistakes that can lead to ATO penalties.
By the end, you’ll know exactly how to complete and lodge your BAS confidently, and how a tax accountant can help you simplify the process and stay fully compliant.
What is a BAS?
A Business Activity Statement (BAS) is a form businesses use to report and pay key tax obligations to the Australian Taxation Office (ATO).
Business Activity Statements usually include:
- Goods and Services Tax (GST)
- Pay As You Go (PAYG) withholding for employees
- PAYG instalments toward your income tax
- And sometimes other taxes like Fringe Benefits Tax (FBT) instalments, Luxury Car Tax (LCT), or Wine Equalisation Tax (WET)
Simply, your BAS tells the ATO how much tax your business owes and how much you’ve already paid.
If you’re wondering why BAS matters, think of it as your business’s regular check-in with the tax office. Lodging it accurately and on time keeps you:
- Compliant
- Avoids penalties
- Ensures your GST credits and tax offsets are correctly applied
Who needs to lodge a Business Activity Statement (BAS) in Australia?
If you’re registered for GST or withhold PAYG tax, you must lodge a BAS to report your business taxes to the ATO.
You must lodge a BAS (usually online) if | Why |
| GST-registered businesses have to report GST, PAYG and other taxes via a BAS. |
You drive taxis or ride-share (Uber, DiDi, etc.). | This sector must register for GST regardless of turnover, so a BAS is compulsory. |
You withhold PAYG tax from employees and the ATO issues you a BAS (rather than the shorter Instalment Activity Statement). | PAYG figures go on the BAS each period. |
In short: If the ATO sends you a BAS, you need to lodge it. Once you’re GST-registered, you’ll keep receiving a BAS every month, quarter or year until you cancel your registration.
How to calculate BAS in Australia
Your BAS sums up the tax you’ve collected and paid throughout the period, mainly your GST on sales minus your GST credits on purchases.
1. GST calculation worksheet
Step | Description | Example figure |
A | Sales (GST-exclusive) | $10,000 |
B | GST collected on those sales (10 %) | $1,000 |
C | Business purchases (GST-exclusive) | $6,000 |
D | GST paid on those purchases | $600 |
Net GST | B – D → the amount you owe (or are owed) | $400 payable |
Tip: Use accounting software to do math for you. At BAS time, just pull the report and you’re ready to lodge.
Read more: Best Accounting Platforms in Australia for 2026
2. BAS statement example (where figures slot in)
BAS Label | What it represents | Amount (AUD) |
G1 | Total sales (inc. GST) | $11,000 |
1A | GST on sales | $1,000 |
G11 | Purchases (inc. GST) | $6,600 |
1B | GST on purchases (credits) | $600 |
9 | Net GST to pay / refund | $400 |
How often do you need to lodge BAS, and when it’s due
Your Business Activity Statement (BAS) lodgement frequency depends on your business turnover and GST reporting cycle. The Australian Taxation Office (ATO) assigns your due dates based on how frequently you report and pay GST, PAYG instalments, and other obligations.
1. Quarterly BAS (most common)
For most small and medium businesses with an annual GST turnover under $20 million.
Due dates:
- Quarter 1 (July – September): 28 October
- Quarter 2 (October – December): 28 February
- Quarter 3 (January – March): 28 April
- Quarter 4 (April – June): 28 July
If you lodge electronically or through a registered BAS/tax agent, you may qualify for extended due dates under the ATO Lodgment Program. These vary by quarter and agent type
2. Monthly BAS
- For businesses with GST turnover ≥ $20 million, or those who voluntarily report monthly for cash-flow tracking.
- Due date:21st of the following month.
(e.g., July BAS → due 21 August.)
3. Annual BAS
- For voluntary GST-registered businesses with turnover under $75 000 ($150 000 for non-profits).
- Due date: With your annual income tax return (usually 31 October).
Even if your business had no sales or purchases, you must still lodge a ‘nil BAS’ to stay compliant. The ATO may apply Failure to Lodge (FTL) penalties and general interest charges. If you can’t lodge or pay on time, contact the ATO or your tax agent early, you can often arrange a payment plan.
Tax Accountant vs Tax Agent: Which One Should You Choose for Your Business?
How to lodge a Business Activity Statement Online with the ATO
When it’s time to lodge your Business Activity Statement, you’ve got a few simple ways to do it: online, through your tax or BAS agent, or by paper form.
But for most businesses, lodging online is the fastest, most reliable way to stay ATO-compliant.
1. Lodge BAS online
Lodging your Business Activity Statement is a two-minute job if you pick the right channel. The ATO gives you four main options:
Method | Best for | How it works | Extra perks / quirks |
Companies, trusts, partnerships | Sign in with your myGovID, head to Lodgments → Activity statements, enter the figures, hit Lodge. | Autosaves and shows all past BAS lodgements. Some online filers may receive later due dates than paper filers, check the ATO’s current schedule, as extensions vary by quarter | |
myGov (ATO online services) | Sole traders and individuals | Log in to myGov, open Tax → Activity statements → Lodge activity statement, complete the form, submit, pay. | Works on your phone; you can also revise previous BAS in the same menu. |
SBR-enabled accounting software | Anyone using Xero, MYOB, QuickBooks, etc. | Reconcile your books, then click File BAS inside the software. The SBR gateway pushes the data straight to the ATO—no re-typing. | Fastest for cloud bookkeeping; you’ll need a machine credential only if you’re on desktop software. |
Registered BAS or tax agent | Businesses that want a pro to handle it | Your agent prepares and lodges through their own portal. You still see each BAS in your online account. | If you lodge through a registered BAS or tax agent, the ATO’s Lodgment Program concessions may extend your due date, usually up to four weeks depending on the quarter. Your agent also handles any ATO follow-ups on your behalf. |
Paper form | Very small number of legacy filers | Complete the original BAS the ATO posts to you and mail it back in the reply-paid envelope. | Slower processing; you need ATO approval to keep using paper long-term. |
Read more: Xero vs Quickbooks: Which Is Better For Your Small Business
2. Log in to ATO Online Services
- If you’re a sole trader, log in via myGov (linked to your ABN) using your myGovID.
- Companies, trusts, and partnerships should use Online Services for Business with a verified myGovID, and authorise their agent using client-to-agent linking (which has replaced the old RAM process)
3. Access your BAS form
- Navigate to ‘Activity Statements’ and open the BAS for the relevant period.
- You’ll see outstanding statements labelled by period end date.
- Some fields may already be prefilled by the ATO.
4. Complete required fields
Use your bookkeeping software or BAS report to fill in:
- G1: Total sales
- 1A: GST on sales
- 1B: GST on purchases (GST credits)
- W1/W2: PAYG withholding (if you have employees)
Double-check every figure, accuracy prevents penalties or delays in GST refunds.
5. Make the declaration
Before lodging, tick the declaration confirming that all information is true and correct, then click Submit.
6. Save your confirmation
Once lodged:
- Save the lodgement receipt or download the BAS as a PDF
- Keep this for your records; it’s your proof if the ATO ever follows up
How to pay your BAS to the ATO
You can pay any amount owing via:
- BPAY using your BAS payment reference number (PRN)
- Direct debit or credit card in ATO Online Services
- Australia Post (in-person or by mail)
Tip: Always confirm your PRN before paying to ensure it’s matched correctly with your statement.
Understanding BAS labels and what they mean
When you complete your Business Activity Statement (BAS), you’ll see a series of labels, each representing a specific tax category the ATO requires you to report.
Here’s a simple breakdown of the most common BAS labels and what they mean:
Label | What it represents | What to include |
G1: Total sales | The total sales or income for the reporting period (including GST) | All taxable, GST-free, and input-taxed sales. |
1A: GST on sales | The GST your business collected from customers. | 10% of taxable sales (excluding GST-free items). |
G11: Non-capital purchases | The total business purchases (excluding GST). | Goods, services, and operating costs excluding capital assets |
1B: GST on purchases | The GST you’ve paid and can claim as input tax credits. | GST paid on business-related purchases |
W1: Total salary, wages and other payments | The total gross wages paid to employees | Include salary, wages, allowances, bonuses, commissions |
W2: Amounts withheld from payments (PAYG withholding | PAYG tax withheld from employee wages. | Amount withheld before paying staff. |
T1: PAYG income tax instalment | Your income tax instalment amount for the period. | Applies if you’re on a PAYG instalment schedule. |
T2: Credit for PAYG instalments | Any PAYG instalment credits that apply. | Reduces the total payable if you’ve paid instalments earlier. |
9: Net amount | The final result: how much you owe the ATO or will be refunded. | Calculated as (GST collected – GST credits ± PAYG instalments). |
Read more: What is PAYG tax and how to calculate it
7 common mistakes to avoid when submitting your BAS
Mistakes on your BAS can lead to delays, penalties, or ATO follow-ups. Avoid these common pitfalls:
- Misreporting GST: Don’t claim GST on GST-free items or input-taxed sales. Check that tax invoices are valid before claiming credits.
- Wrong wage and PAYG figures: Double-check wages (W1) and withholding (W2) amounts, especially if you pay directors or contractors.
- Missing cash sales: Report all income, even if it wasn’t invoiced or went through EFTPOS.
- Incorrect PAYG installments: If you’re paying income tax in installments, use the correct amount, either calculated or pre-filled by the ATO.
- Fuel tax credit errors: Only claim what you’re entitled to, and make sure the fuel usage and business purpose are clearly documented.
- Simple data entry slip-ups: Watch for typos, misplaced decimals, or wrong figures, and review everything before submitting.
- Lodging late: Set calendar reminders well before the due date and keep your records in shape. Late lodgements often mean penalties and missed refund opportunities.
How a tax accountant helps you lodge BAS accurately (and avoid penalties)
Lodging your BAS isn’t just about ticking boxes; it’s about making sure every number is accurate and every credit is claimed. That’s where a registered tax accountant makes all the difference.
Here’s how they help your business stay compliant and confident:
- Ensure accuracy and ATO compliance: They check your GST, PAYG, and instalment data before lodgement to prevent costly mistakes.
- Maximise your GST credits: Accountants make sure you claim every eligible credit while staying within ATO rules.
- Avoid late lodgement penalties: Registered agents can extend BAS deadlines and manage your lodgement schedule for you.
- Improve cash flow planning: They forecast your BAS payments so you can plan ahead instead of scrambling at the last minute.
- Handle ATO correspondence: From follow-ups to clarification requests, they deal directly with the ATO, so you don’t have to.
A tax accountant is more than a number checker, they’re your compliance partner, helping you lodge accurately, claim confidently, and stay penalty-free every quarter
How Sleek helps with BAS lodgement and compliance
Handling BAS lodgements, PAYG instalments, and GST calculations can quickly become overwhelming, especially when you’re running a business. That’s where Sleek’s expert tax accountants step in to make BAS management simple, accurate, and fully compliant.
Here’s how Sleek helps you take control of your business tax:
- Complete BAS and tax compliance, handled for you
From preparing and reviewing your BAS to lodging it directly with the ATO, our accountants ensure every figure aligns with your GST, PAYG, and income tax obligations. - Real-time bookkeeping that keeps your BAS accurate
We reconcile your transactions throughout the quarter, so your BAS lodgement is backed by clean, audit-ready records, no last-minute panic or missed credits. - Strategic tax advice that saves you money
Our accountants go beyond data entry, we help you identify legitimate GST credits, review PAYG instalments, and optimise deductions across your BAS and tax returns. - ATO correspondence and audit support
If the ATO requests clarification or conducts a review, our team handles the communication, so you can focus on your business, not paperwork.
With Sleek, your BAS isn’t just submitted, it’s strategically managed as part of your overall tax compliance and business growth strategy.
Simplify your BAS, streamline your accounting, and stay ATO-compliant, all in one place. Talk to a Sleek tax accountant today and take the stress out of BAS once and for all.
FAQs on what is a Business Activity Statement (BAS)
You must keep all BAS-related records for at least five years from when they’re prepared, obtained, or the transaction is completed, whichever is later.
This includes:
- Tax invoices and receipts for sales and purchases
- Bank statements, payroll records, and PAYG summaries
- BAS lodgement receipts and ATO payment confirmations
- Accounting software reports showing how figures were calculated
Digital records are fully acceptable as long as they’re complete, legible, and retrievable if the ATO requests them.
Yes, you generally can, but only for certain expenses and within four years of the purchase.
Eligible items include stock on hand, trading assets, and business equipment still used in your business. Keep tax invoices and ensure the purchases were made for business use.
If you’ve discovered an error, like claiming the wrong GST credit or omitting a sale, you can usually correct it in your next BAS (within the ATO’s adjustment limits).
Larger or older errors must be corrected through an amended BAS. Your accountant can help determine which approach applies to stay compliant.
A BAS (Business Activity Statement) reports GST, PAYG withholding, and other taxes. An IAS (Instalment Activity Statement) is used when you’re not registered for GST but still need to report PAYG or other obligations.
incorporation, accounting, tax
services, and compliance.
450,000
businesses worldwide.
from 4,100+ reviews.
satisfaction rate from
16,000 surveyed clients.
450,000
businesses worldwide.
from 4,100+ reviews.
satisfaction rate from
16,000 surveyed clients.
