How to Lodge a BAS in Australia: Complete 2026 Guide

What Is a Business Activity Statement (BAS)?

A Business Activity Statement, or BAS, is a form submitted to the Australian Taxation Office (ATO) that reports your business's tax obligations. If you're registered for GST, PAYG withholding, PAYG instalments, or fringe benefits tax, you'll need to lodge a BAS — no exceptions.

Think of it as your regular check-in with the ATO. You're telling them how much GST you collected, how much you paid, and what other tax obligations you've met during the period.

Who Needs to Lodge a BAS?

You must lodge a BAS if your business is:

• Registered for GST — mandatory if your annual turnover is $75,000 or more ($150,000 for not-for-profits)
• Required to withhold PAYG from employee wages
• Paying PAYG instalments on business or investment income
• Liable for fringe benefits tax (FBT) instalments

Even if you voluntarily registered for GST below the threshold, you still need to lodge.

Quarterly vs Monthly: Which BAS Schedule Are You On?

Most small businesses lodge quarterly, but the ATO may require monthly lodgement if:

• Your annual GST turnover is $20 million or more
• You've elected to report monthly

Quarterly BAS Due Dates for 2026

Tip: If you lodge through a registered tax agent or BAS agent, you may receive extended deadlines.

Step-by-Step: How to Lodge Your BAS

Step 1: Gather Your Records

Before you start, make sure you have:

• All sales invoices for the period
• Purchase receipts and supplier invoices
• Bank statements reconciled
• Payroll records (if reporting PAYG withholding)
• Any adjustment notes or credit notes

Keeping your records organised throughout the quarter makes this step dramatically easier. If you're using accounting software like OneBookPlus, your sales and expense data is already categorised and ready to go.

Step 2: Calculate Your GST

There are two methods for reporting GST:

• Cash basis — report GST when you actually receive or make payments
• Accrual basis — report GST when you issue or receive invoices, regardless of payment

Most small businesses use the cash basis. Your BAS will require:

• 1A: GST on sales (GST you collected)
• 1B: GST on purchases (GST you paid)

The difference is what you owe the ATO (or what they owe you).

Step 3: Complete PAYG Fields (If Applicable)

If you withhold tax from employee wages, you'll also report:

• W1: Total wages paid
• W2: Amount withheld

If you pay PAYG instalments on your own income:

• T1/T2: Instalment income and amount

Step 4: Lodge with the ATO

You can lodge your BAS through:

• myGov/ATO online services — log in, navigate to BAS, and enter your figures
• Online through your accounting software — many platforms offer direct ATO lodgement
• Through your BAS or tax agent — they handle everything for you
• By paper — still accepted, but the ATO strongly encourages online lodgement

Step 5: Pay Any Amount Owing

If you owe GST or PAYG, payment is due by the same deadline as your lodgement. Payment options include:

• BPAY
• Direct debit
• Credit/debit card (fees apply)
• At Australia Post

If you can't pay in full, contact the ATO to set up a payment plan before the due date. This shows good faith and may reduce penalties.

Common BAS Mistakes to Avoid

1. Claiming GST on GST-Free Items

Not everything attracts GST. Fresh food, medical services, education, and some financial services are GST-free. Double-check your claims.

2. Forgetting to Reconcile

Lodging a BAS from unreconciled records is a recipe for errors. Always reconcile your bank feeds first.

3. Mixing Personal and Business Expenses

Only claim GST credits on legitimate business expenses. The ATO's data-matching capabilities are more sophisticated than ever.

4. Missing the Deadline

Late lodgement attracts a penalty of $313 for each 28-day period (or part thereof) that the BAS is overdue, up to a maximum of $1,565. Set calendar reminders or use software that alerts you.

5. Not Keeping Records for 5 Years

The ATO requires you to retain all business records for at least five years. Digital copies are perfectly acceptable — just make sure they're backed up.

How to Simplify BAS Reporting

The single best thing you can do is stay on top of your bookkeeping throughout the quarter. When BAS time rolls around, you should be reviewing and confirming numbers, not scrambling to enter three months of receipts.

Here's what makes the process painless:

• Record expenses as they happen — snap a photo of receipts and log them immediately
• Reconcile weekly — don't let transactions pile up
• Use software that tracks GST automatically — every invoice and expense should have GST calculated and categorised
• Separate GST-free and GST-inclusive transactions — your software should handle this, but double-check

How OneBookPlus Makes BAS Easier

OneBookPlus automatically calculates GST on every invoice and expense you create. At BAS time, you can pull up your GST summary report that shows exactly what you collected (1A) and what you paid (1B) for the period.

Key features that help with BAS:

• Automatic GST calculations on all invoices and expenses
• GST summary reports broken down by period
• Bank reconciliation to ensure nothing is missed
• Receipt capture so you never lose a deduction
• BAS deadline reminders so you never lodge late

Get Started

If you're still tracking GST in spreadsheets or shoeboxes, it's time to upgrade. OneBookPlus offers a free plan that includes invoicing, expense tracking, and GST reporting — everything you need to lodge your BAS with confidence. Sign up at onebookplus.com.au and take the stress out of your next BAS.