BAS Lodgement Guide: How to Prepare Your Quarterly BAS

If you’re a sole trader or small business owner registered for GST in Australia, you need to lodge a Business Activity Statement every quarter. For many people, BAS time means stress – hunting for receipts, trying to remember which purchases included GST, and hoping the numbers add up. But preparing your quarterly BAS doesn’t have to be a scramble. With the right approach and consistent record-keeping, it can be a straightforward process that takes an hour or less.

Disclaimer: This article provides general information only and does not constitute tax advice. Consult a registered tax agent for advice specific to your circumstances.

What Is a BAS?

A Business Activity Statement is a form you lodge with the ATO to report and pay several tax obligations, including GST collected on your sales, GST paid on business purchases (input tax credits), PAYG withholding (if you have employees), and PAYG instalments (if applicable). For most sole traders, the BAS is primarily about GST: reporting what you’ve collected, what you’ve paid, and settling the difference.

The ATO provides more detail on BAS requirements at their activity statements page.

Who Needs to Lodge a BAS?

You need to lodge a BAS if you are registered for GST. GST registration is compulsory if your business has a GST turnover (gross income from all your business activities) of $75,000 or more per year. If your turnover is below that threshold, you can choose to register voluntarily.

If you’re not registered for GST, you don’t need to lodge a BAS – but you also can’t charge GST on your sales or claim GST credits on your purchases.

Once you’re registered, you must lodge a BAS even in quarters where you had no sales or purchases. A nil BAS is still required.

Quarterly BAS Deadlines

Quarterly BAS lodgement follows the standard Australian financial quarters. The due dates are the 28th of the month after each quarter ends:

Note that the Q2 deadline is 28 February, not 28 January – the ATO provides an extra month for the December quarter.

If you use a registered BAS agent, you may receive a later lodgement deadline. Check with your agent for the specific due dates that apply to you.

Missing the deadline carries penalties. The ATO charges a failure-to-lodge penalty for each 28-day period (or part thereof) that your BAS is late. Penalties start at one penalty unit and can accumulate up to five penalty units.

What You Need to Report

The key figures on your quarterly BAS are:

G1: Total Sales

This is your total sales for the quarter, including GST-free and input-taxed sales. It’s your gross income from all business activities.

1A: GST on Sales

The total GST you collected on your sales. If all your sales are GST-inclusive (the standard for most sole traders), this is your total sales divided by 11.

1B: GST on Purchases

The total GST you paid on your business purchases – your input tax credits. This is where your receipt records matter. You can only claim GST credits if you have a valid tax invoice for each purchase.

The Net Amount

The difference between 1A (GST collected) and 1B (GST paid) determines whether you owe the ATO or receive a refund:

• If 1A is greater than 1B, you owe the difference to the ATO
• If 1B is greater than 1A, the ATO owes you a refund

For example, if you collected $5,000 in GST on sales and paid $3,200 in GST on purchases, you owe $5,000 - $3,200 = $1,800 to the ATO.

How to Prepare Your BAS – Step by Step

Step 1: Reconcile Your Receipts

Before you calculate anything, make sure all your receipts for the quarter are captured and categorised. Go through your records and check:

• Are all business purchases recorded?
• Is the GST amount correctly separated from the total on each transaction?
• Are there any expenses you’ve missed – cash purchases, small online subscriptions, parking, tolls?
• Are all receipts assigned to the correct quarter?

If you’ve been scanning receipts consistently throughout the quarter, this step takes minutes. If you’ve fallen behind, this is where the pain starts.

Step 2: Check Your GST Totals

Review your GST figures for accuracy:

• GST collected: Cross-reference against your sales invoices or point-of-sale records. Make sure you’re reporting all GST-inclusive sales, not just the ones where customers paid on time.
• GST paid: Check that you’ve only claimed GST credits on purchases that actually included GST. Common GST-free items that trip people up include most basic food, some health services, and purchases from suppliers who aren’t registered for GST.

A useful sanity check: your total GST on purchases (1B) should be roughly proportional to your total business spending. If the GST figure looks unusually high or low relative to your expenses, dig into the details.

Step 3: Generate Your Report

Export a quarterly report showing:

• Total sales for the quarter
• Total purchases for the quarter
• GST collected on sales
• GST paid on purchases
• Net GST position (what you owe or are owed)

This report is what you (or your BAS agent) will use to complete the BAS form.

Step 4: Lodge and Pay

You can lodge your BAS through:

• myGov – linked to your ATO online services
• Your accounting software – many packages can lodge directly
• Your BAS agent – they can lodge on your behalf
• The ATO’s online services for business – if you have an AUSkey or myGovID

If you owe GST, payment is due on the same date as lodgement. You can pay via BPAY, direct debit, credit card, or at a post office.

Common BAS Mistakes to Avoid

These are the errors that the ATO sees most often – and that cost sole traders money or trigger audits.

Claiming GST on GST-free items

Not all purchases include GST. Common GST-free items include most basic food, some education services, some medical services, and exports. If a receipt doesn’t show a GST amount, don’t claim a GST credit for it. Overclaiming GST credits is a red flag for the ATO.

Forgetting to include all sales

Your BAS must report all sales, not just the ones that have been paid. If you invoiced a client in March but they didn’t pay until April, the sale is still reported in the Q3 BAS (unless you use cash basis accounting – check with your accountant which method you’re on).

Not reconciling before lodging

Lodging without reconciling against your bank statements is a recipe for errors. Spend ten minutes cross-checking your reported figures against actual bank transactions to catch missed expenses and double-counted items.

Missing the deadline

Late lodgement penalties are avoidable. Set a reminder for two weeks before each due date. If you know you’ll miss a deadline, contact the ATO beforehand – they may grant an extension.

Guessing the GST split

If you can’t find the receipt, don’t guess the GST amount. The ATO requires a valid tax invoice to claim a GST credit. Without one, the credit can’t be claimed.

How Taxr Simplifies BAS Preparation

Taxr is built to make quarterly BAS preparation fast and accurate. Here’s how it helps:

• GST auto-extracted – when you scan a receipt, the AI identifies and extracts the GST amount separately from the total. No manual calculation, no dividing by 11.
• Categories aligned to ATO labels – your expenses are categorised using the same labels the ATO expects, so your records are BAS-ready from the moment you scan.
• Quarterly export – select the quarter’s date range and export a clean report with GST totals. Hand it to your BAS agent or use it to complete your BAS yourself.
• No missing receipts – because you scan receipts the moment you get them, there’s nothing to chase at BAS time. Every expense is captured, categorised, and stored.

For more on GST tracking and what counts as a valid tax invoice, see our detailed guide to GST receipt tracking for Australian businesses. And for a broader view of expense tracking best practices, our post on how to track business expenses as a sole trader covers the fundamentals.

Make Your Next BAS the Easiest One Yet

BAS preparation doesn’t have to be a quarterly crisis. The secret is consistent record-keeping throughout the quarter, not a last-minute scramble in the final week. Scan your receipts as you go, let the AI handle the GST extraction, and when the deadline approaches, export your report and lodge with confidence.

Start building the habit today. Download Taxr and take the stress out of your quarterly BAS.