BAS Guide: Everything Australian Businesses Need to Know

What Is a Business Activity Statement (BAS)?

A Business Activity Statement is a form submitted to the Australian Taxation Office (ATO) that reports your tax obligations for a given period. If your business is registered for GST, you must lodge a BAS - there are no exceptions.

Your BAS reports several things, but the most common are:

• Goods and Services Tax (GST) collected on sales and paid on purchases
• Pay As You Go (PAYG) withholding from employee wages
• PAYG instalments for your own income tax
• Fringe Benefits Tax (FBT) instalments if applicable

Most small businesses primarily deal with the GST component, but understanding all sections ensures you report correctly.

Who Needs to Lodge a BAS?

You must lodge a BAS if your business is registered for GST. GST registration is mandatory if your annual turnover is $75,000 or more ($150,000 for not-for-profit organisations). Businesses with turnover below this threshold can voluntarily register for GST.

Even if you had no business activity during a period, you still need to lodge a nil BAS. Failing to lodge results in penalties that compound over time.

BAS Lodgement Frequency

The ATO offers three lodgement frequencies:

Monthly BAS

Required if your annual turnover exceeds $20 million. Due on the 21st of the month following the reporting period. For example, your January BAS is due by 21 February.

Quarterly BAS

The most common frequency for small businesses. Due dates are:

• Q1 (July-September): 28 October
• Q2 (October-December): 28 February
• Q3 (January-March): 28 April
• Q4 (April-June): 28 July

If you lodge through a registered tax agent or BAS agent, you may receive an extended due date.

Annual BAS

Available for businesses with turnover under $10 million that report GST annually. Less common, but useful for very small operations.

How to Calculate Your GST for BAS

There are two methods for reporting GST on your BAS:

Cash Basis

You report GST when you actually receive payment or make payment. This is simpler and better for cash flow because you only pay GST on money you have already received.

Accrual Basis

You report GST when you issue an invoice or receive a bill, regardless of when payment occurs. This is required for businesses with turnover above $10 million but optional for smaller businesses.

Most small businesses choose the cash basis because it aligns GST obligations with actual cash flow.

Step-by-Step: Completing Your BAS

1. Reconcile Your Accounts

Before preparing your BAS, ensure all bank transactions for the period are reconciled and correctly categorised. Every transaction needs the right GST code - this is where most errors occur.

2. Review GST Codes

Check that your transactions have the correct GST treatment:

• GST (G1): Standard goods and services at 10%
• GST-Free (G2): Items that are GST-free (basic food, medical services, exports)
• Input Taxed (G3): Financial services and residential rent
• No GST: Transactions outside the GST system (wages, bank transfers)

3. Calculate Totals

Your BAS calculates the difference between GST collected on sales (1A) and GST paid on purchases (1B). If you collected more than you paid, you owe the ATO. If you paid more than you collected, you receive a refund.

4. Report PAYG Withholding

If you have employees, report the total PAYG withheld from wages during the period. This should match your payroll records exactly.

5. Lodge and Pay

Lodge electronically through the ATO Business Portal, your accounting software (Xero supports direct BAS lodgement), or through your registered agent.

Common BAS Mistakes to Avoid

Incorrect GST codes are the number one source of BAS errors. A coffee meeting coded as GST-free instead of GST, or an export coded with GST when it should be GST-free - these small errors add up.

Missing transactions from the period. If you reconcile late, transactions from the BAS period might slip into the next period.

Claiming GST on non-deductible items like personal expenses, entertainment without a clear business purpose, or items purchased before GST registration.

Forgetting to lodge a nil BAS when you had no activity. The ATO still expects a lodgement.

Not keeping proper records to support your claims. The ATO requires you to keep records for five years. If audited, you need to prove every claim.

Automating BAS Preparation

Manual BAS preparation is time-consuming and error-prone. Modern tools like SortBooks automate the process by:

• Automatically applying correct GST codes to every transaction based on AI categorisation
• Generating BAS-ready reports that summarise your GST position
• Flagging transactions with unusual or missing GST codes for review
• Keeping a complete audit trail for ATO compliance

The goal is to make BAS lodgement a 15-minute review process rather than a multi-day ordeal.

Late Lodgement Penalties

The ATO charges a Failure to Lodge (FTL) penalty for late BAS lodgements. The penalty is calculated per 28-day period (or part thereof) that the BAS is overdue:

• Small entities: $313 per period
• Medium entities: $626 per period
• Large entities: $1,565 per period

These penalties can be remitted if you have a good compliance history and the delay was due to circumstances beyond your control. However, the best approach is simply to lodge on time.

Key Takeaways

1. Lodge your BAS on time, every time - even if it is a nil lodgement
2. Use the cash basis if your turnover is under $10 million
3. Reconcile all transactions before preparing your BAS
4. Double-check GST codes on every transaction
5. Keep records for five years
6. Consider automating BAS preparation to reduce errors and save time