What is a BAS and how do you lodge it?

Tax season can feel overwhelming when you're running a business in Australia. Understanding what a BAS is is the first step to staying compliant and avoiding costly penalties. This post covers what a business activity statement (BAS) is, who needs to lodge one, and how to do it correctly.

What is a business activity statement (BAS)?

A business activity statement (BAS) is a form you submit to the Australian Taxation Office (ATO). It is used to report and pay your tax obligations for a set period. The ATO sends your BAS automatically once you’re registered for GST. You must lodge it even if you have nothing to report. This is called a ‘nil’ BAS.

The form includes sections for GST, PAYG withholding, PAYG instalments, and other taxes. So what does a BAS look like? It’s a pre-printed form with your ABN, a document ID, and a series of labelled fields. Each label corresponds to a different tax obligation you need to fill in or confirm.

What does a BAS include?

The BAS activity statement form has several sections. Each section covers a different tax type. Here’s a breakdown of what you’ll typically see on a BAS.

Goods and Services Tax (GST)

GST is a 10% tax on most goods and services sold in Australia. You report how much GST you collected from customers. You also report how much you paid on business expenses. The difference tells you whether you owe the ATO or are owed a refund.

PAYG withholding

If you employ staff, you must withhold tax from their wages. This is pay as you go (PAYG) withholding. You report these amounts on your BAS and pay them directly to the ATO each period.

PAYG instalments

PAYG instalments are prepayments of your own income tax. The ATO uses your previous year’s income to set your instalment amount. If you’re not registered for GST, you may use an Instalment Activity Statement (IAS) instead.

Other taxes

The BAS can also include fringe benefits tax (FBT), luxury car tax, wine equalisation tax, and fuel tax credits. These only apply if your business activities trigger them. Not every business will need to complete all of these sections.

Who needs to lodge a BAS?

You need to lodge a BAS if you’re registered for GST. GST registration becomes compulsory once you reach the $75,000 turnover threshold. Not-for-profit bodies have a threshold of $150,000 instead.

Sole traders, companies, trusts, and partnerships all need to register if they exceed this threshold.

Even businesses below the threshold can register voluntarily. Once registered, you’ll receive a BAS, and you must lodge it. You’ll need your ABN to register and to lodge your statements with the ATO.

BAS lodgement frequencies

Your lodgement frequency depends on your turnover and ATO direction. There are 3 main options available to businesses.

Quarterly lodgement 

Quarterly lodgement applies to most small and medium businesses. It’s the default for businesses with a GST turnover under the $20 million threshold. You lodge 4 times a year, due 28 days after quarter end.

Monthly lodgement

If your GST turnover reaches or exceeds $20 million, you must lodge monthly. You can also choose to lodge monthly voluntarily. This can help you manage cash flow through smaller, more regular payments.

Annual lodgement

If you’re voluntarily registered and earn under $75,000, you may elect to report annually. The deadline for annual lodgement is 31 October. This option suits very small businesses with straightforward tax affairs.

BAS due dates and deadlines

Your specific due date always appears on your BAS document. Quarterly BAS is generally due 28 days after each quarter ends. Monthly BAS is typically due on the 21st of the following month.

If the due date falls on a weekend or public holiday, you get until the next business day. Lodging through a registered tax agent or BAS agent may give you extended deadlines. Contact the ATO before the due date if you can’t lodge or pay. Late lodgement triggers penalties and interest charges.

How to prepare your BAS: What you need

Good preparation makes lodgement much easier. Before you start, pull together your key documents, including the following:

• Your ABN and BAS document ID, found in the top right corner of your statement
  
• Sales and purchase records for the reporting period
  
• Payroll records, including all PAYG withholding amounts
  

You’ll also need supporting financial records, including bank statements to reconcile against your books and invoices and receipts to support your GST credit claims. The ATO expects all businesses to keep organised financial records. Using SBR-enabled accounting software speeds this up and cuts down on errors.

How to lodge your BAS: Step by step

Knowing the answer to "What is a BAS?" is one thing. Knowing how to lodge it is another. You have 4 main options when it comes to lodging.

Option 1: Lodge online via ATO Online Services

Log in to ATO Online Services using your myGovID. Sole traders access this via myGov. Companies, trusts, and partnerships use Online Services for Business.

Your BAS will appear in the ‘For action’ panel. Fill in the required fields, review your figures, tick the declaration, and submit. You’ll get a unique receipt ID on confirmation.

Option 2: Lodge through accounting software

Many businesses use SBR-enabled accounting software that connects directly to the ATO. Once your figures are reconciled, you can lodge without leaving the platform. This reduces manual data entry and lowers the risk of errors. It also keeps your records and lodgement history together in one place.

Option 3: Lodge through a registered tax agent or BAS agent

A registered tax agent or BAS agent can lodge the BAS on your behalf. This suits businesses with complex tax affairs or those who want professional oversight.

Agents often qualify you for extended deadlines under the ATO Lodgment Program. They can also help you set up a payment plan if you’re struggling to pay in full.

Option 4: Lodge by paper form

You can also request a paper form from the ATO and return it by post. This is slower and less common today. Paper lodgers don’t qualify for the extended deadlines available to online lodgers.

You should only use this method if you have no online access.

The benefits of lodging your BAS online

Online lodgement is faster, more secure, and more reliable than paper. The ATO emails you a reminder 21 days before your BAS is due.

Online lodgement gives you access to your lodgement history for up to 4 years. You can review, revise, and print statements directly from the portal. It also speeds up processing if you’re owed a GST refund.

Common BAS lodgement mistakes to avoid

Mistakes on your BAS can trigger ATO follow-ups, penalties, and delays. Here are the 5 most common errors to watch for.

Lodging late

Missing your due date results in failure to lodge (FTL) penalties. These accrue over time and can become significant. If you can’t lodge on time, contact the ATO immediately to discuss your options.

Reporting incorrect GST amounts

Claiming GST on GST-free or input-taxed items is a frequent error. Missing GST credits you’re entitled to claim is another. Always reconcile your figures against your records before submitting.

Claiming ineligible deductions

Not every business expense qualifies for a GST credit. Personal expenses or purchases without a valid tax invoice don’t qualify. Review each claim carefully before including it on your BAS.

Failing to reconcile accounts

Your BAS figures must match your financial records. Discrepancies mean you may be reporting inaccurate amounts. Make reconciliation a regular part of your bookkeeping, not just a BAS-time task.

Poor record keeping

The ATO requires businesses to keep records for at least 5 years. Poor record-keeping is one of the most common audit triggers. Digital systems make it far easier to store and retrieve what you need.

Best practices for a stress-free BAS lodgement

Staying on top of your BAS doesn’t have to be stressful. A few consistent habits make a real difference. Here are a few key recommendations:

• Set aside GST and PAYG amounts regularly so funds are ready at lodgement time.
  
• Reconcile your accounts each month, not just at BAS time.
  
• Use SBR-enabled accounting software to reduce manual entry and errors.
  
• Keep digital copies of all invoices, receipts, and payroll records.
  
• Diarise your BAS due dates at the start of the financial year.
  
• Work with a BAS agent or registered tax agent if your situation is complex.
  

This proactive approach means fewer surprises and a cleaner compliance record with the ATO.

FAQs

Here are answers to some common questions about BAS lodgement.

What is the difference between a BAS and an IAS?

A BAS covers GST, PAYG withholding, and other taxes. An instalment activity statement (IAS) covers only PAYG instalments for businesses not registered for GST.

What happens if I lodge my BAS late?

Lodging your BAS late can result in failure to lodge (FTL) penalties. General interest charges accrue until you lodge and pay in full.

Can I set up a payment plan if I can’t pay my BAS?

If you can’t pay your BAS in full, contact the ATO early to arrange a payment plan. Interest charges may still apply during the arrangement.

What is a BAS and who must lodge it?

A business activity statement (BAS) is a form businesses submit to the Australian Taxation Office. Any business registered for GST must lodge a business activity statement. This reports and pays taxes, including GST and PAYG, to the ATO.