How to Lodge Your BAS Online in Australia — Step by Step

Q: Can I get more time to lodge my BAS?

Businesses that use a registered BAS agent benefit from extended lodgement dates through the ATO's lodgement program — in some cases a month or more of extra time.

Q: What is the difference between a BAS agent and a tax agent?

A BAS agent is registered specifically for BAS services. A tax agent can additionally provide income tax advice. Optium Accountants is registered as both.

If your business is registered for GST, lodging your Business Activity Statement (BAS) is one of your most important recurring compliance obligations. The good news: you can do it entirely online through the ATO Business Portal or myGov — no paper forms required. This guide walks you through every step, from preparation to payment.

What Is a BAS and Who Needs to Lodge It?

A Business Activity Statement (BAS) is a form submitted to the Australian Taxation Office (ATO) to report and pay your business tax obligations for a given period. If your business has a GST turnover of $75,000 or more per year — or $150,000 for non-profit organisations — you must register for GST and lodge a BAS.

Taxi and ride-share drivers must register for GST regardless of turnover.

Your BAS consolidates several tax obligations into one form, including:

GST collected on your sales and income
GST credits (input tax credits) on your business purchases
PAYG withholding — tax withheld from employee wages
PAYG instalments — prepaid income tax if applicable
FBT instalments — if your business pays fringe benefits

Before You Start — What You'll Need

Gather the following before you sit down to lodge your BAS online:

✓ myGov account or ATO Business Portal access

You need to log in through myGov (individuals) or the ATO Online Services for Business portal.

✓ GST sales total for the period

Total sales including GST collected. From your accounting software, this is typically your total taxable sales.

✓ GST purchases total for the period

Total business purchases on which you paid GST — your input tax credits.

✓ PAYG withholding amounts

If you have employees, total PAYG tax withheld from their wages for the period.

✓ Accounting software reports

GST summary reports from Xero, QuickBooks, MYOB, or Wave showing your BAS figures, already reconciled.

✓ Your ABN and GST registration details

You will need your Australian Business Number and lodgement period reference from the ATO.

Step 1: Access Your BAS Online

There are two main ways to lodge your BAS online in Australia:

Option A — myGov (for individuals and sole traders)

Go to myGov and sign in to your account.
Click on the ATO service tile (you must have linked the ATO to your myGov account).
Select Tax > Activity statements.
Find the BAS for the relevant period and click Prepare.

Option B — ATO Online Services for Business (for companies, trusts, partnerships)

Go to the ATO's Online Services for Business portal.
Sign in with your myGovID credentials (you must have a Standard or Strong identity strength).
Navigate to Activity statements.
Select your BAS period and click Prepare now.

Note: If you lodge through accounting software like Xero or QuickBooks, your software may lodge directly via the ATO's API — meaning you never need to visit the portal at all. Check with your software provider.

Step 2: Calculate Your GST

Before entering figures into your BAS, you need to calculate your net GST position for the period:

GST Calculation Formula

GST on sales (G1 ÷ 11) = GST collected

GST on purchases (G11 ÷ 11) = GST credits (ITCs)

GST collected − GST credits = Net GST amount payable (or refundable)

Most accounting software calculates this automatically. Run a GST Detail report in Xero, QuickBooks, or MYOB for the BAS period to get your figures. Always reconcile the software figures against your bank statement before proceeding.

Step 3: Complete the BAS Fields

The online BAS form has labelled boxes. Here are the key fields and what goes in them:

Field	What to Enter
G1 — Total sales	Total value of all sales and income for the period (including GST where applicable)
G2 — Export sales	Sales to overseas customers — these are GST-free
G3 — Other GST-free sales	GST-free domestic sales (food, medical, education, etc.)
G10 — Capital purchases	Business capital items purchased that include GST
G11 — Non-capital purchases	All other business purchases that include GST
1A — GST on sales	Calculated: GST collected on your taxable sales
1B — GST on purchases	Calculated: GST credits (input tax credits) on eligible purchases

The ATO system automatically calculates net GST (1A minus 1B). If 1A > 1B, you owe GST. If 1B > 1A, you receive a GST refund.

Step 4: Report PAYG Withholding & Instalments

If you have employees, report the PAYG withholding amounts withheld from their wages in the relevant W fields. If you pay PAYG income tax instalments, enter the instalment amount in T fields. These amounts are added to your net GST to calculate the total amount payable.

W1 — Total salary, wages, and other payments
W2 — Amount withheld from wages (PAYG tax)
W4 — PAYG withholding from investment distributions (if applicable)
T1 — PAYG instalment income (if using instalment income method)
T4 — PAYG instalment amount (if using instalment amount method)

Step 5: Review and Submit

Before submitting, review every field against your accounting software reports. Check:

GST figures match your reconciled software report
No figures are transposed or entered in the wrong box
PAYG withholding matches your payroll records and Single Touch Payroll (STP) data
Total amount payable makes sense given your business activity for the period

Once satisfied, click Submit. The ATO will send a confirmation and display the amount owing (or refund due). Keep a copy of the lodgement confirmation for your records.

Step 6: Pay Any Amount Owing

If your BAS shows an amount owing, you must pay by the due date to avoid general interest charges (GIC). Payment options include:

BPAY — using the biller code and reference number on your BAS notice
ATO Online Services — pay directly through the portal by card or bank transfer
Direct debit — set up an ATO payment plan if you cannot pay in full
Electronic funds transfer (EFT) — to the ATO's bank account using the correct reference

If you cannot pay on time, contact the ATO before the due date to arrange a payment plan. Acting proactively almost always results in better outcomes than ignoring the debt.

Common BAS Lodgement Mistakes to Avoid

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Entering GST-inclusive amounts instead of exclusive amounts

The BAS fields for G1, G10, and G11 expect the total sales/purchase amount including GST — the system calculates the GST component. Some people enter the ex-GST figure instead, understating their GST collected.

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Claiming ITCs on non-business purchases

GST credits (input tax credits) are only claimable on purchases used for your business. Private expenses, even if paid from a business account, cannot be claimed.

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Claiming ITCs on GST-free or exempt supplies

No GST means no credit. Bank fees, ATO charges, wages, and some insurance premiums don't include GST — you can't claim ITCs on these.

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Forgetting to reconcile before lodging

Always reconcile your BAS figures against your bank statement. Unreconciled transactions can lead to over- or under-reporting GST.

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Lodging late

Self-lodgers have a shorter window than registered agent clients. Missing deadlines triggers FTL penalties which compound over time.

When to Use a Registered BAS Agent

While self-lodgement is possible, many Melbourne small business owners find it's not worth the risk — particularly as the business grows. Consider engaging a registered BAS agent like Optium Accountants if:

Your BAS regularly shows errors or requires correction
You have complex GST transactions — property, exports, mixed supplies
You don't have time to reconcile accounts before each deadline
You want access to extended ATO lodgement dates
You've received ATO queries or are concerned about compliance
Your business is growing and BAS complexity is increasing

Optium Accountants — Melbourne BAS Agents

Optium Accountants are registered BAS agents in Melbourne, serving small businesses since 2007. We prepare and lodge BAS within 24 hours of receiving your records, reconcile your GST accounts, and handle all ATO correspondence — so you can focus on your business.

Learn about our BAS & GST Services →

Frequently Asked Questions

Can I lodge my BAS through Xero or QuickBooks?

Yes. Both Xero and QuickBooks can lodge BAS directly to the ATO via their integrated lodgement feature. You prepare the BAS in the software and submit it directly — no need to log into the ATO portal separately. You still need to reconcile your accounts before lodging.

What if I make a mistake on a lodged BAS?

You can correct minor errors on your next BAS up to certain thresholds. For larger errors, you may need to amend the original BAS. Contact Optium Accountants or the ATO to discuss the best approach for your situation.

Do I need to lodge a BAS if my turnover is below $75,000?

If you voluntarily registered for GST even though your turnover is below $75,000, you must lodge a BAS. If you are not registered for GST, you don't need to lodge a BAS — though you may still have other tax obligations.

Can I get more time to lodge my BAS?

Self-lodgers must meet the standard ATO deadlines (typically 28 days after the end of each quarter). Businesses that use a registered tax agent or BAS agent benefit from extended lodgement dates through the ATO's lodgement program — in some cases a month or more of extra time.

What is the difference between a BAS agent and a tax agent?

A BAS agent is registered specifically to provide BAS services — GST, PAYG, and related lodgements. A tax agent is also registered and can additionally provide income tax advice and prepare income tax returns. Optium Accountants is registered as both, providing comprehensive services.