Preparing Your BAS from Bank Statement Data

Your Business Activity Statement (BAS) reports GST, and sometimes PAYG and other obligations, to the Australian Taxation Office (ATO). For many small businesses, the bank account is where most of the activity lives, so it is a sensible starting point for gathering the figures. This guide walks through a workflow that begins with raw bank statement data and ends with numbers you can transfer onto the BAS form.

One thing to be clear about up front: the bank statement is a starting point, not the whole story. Cash sales, transactions through a separate payment processor, and non-cash adjustments will not appear in your bank feed. Treat the steps below as a way to capture the bulk of your activity, then fill the gaps from your other records.

Step 1: Export and convert your statements

Pull the statements that cover the BAS period — monthly or quarterly, depending on your reporting cycle. Most banks supply them as PDFs, which are awkward to total or filter. Convert each statement into a spreadsheet so you can sort, tag, and add up rows. You can do this with the bank statement converter or by following our guide on how to convert a bank statement to Excel.

Aim for one clean sheet per account with columns for date, description, debit, credit, and a blank column for the category you will assign next. If you run more than one business account, bring them all into the same workbook so nothing is missed.

Step 2: Categorize sales versus expenses

Go down the transaction list and label each line. At the simplest level you are separating money in (sales and other income) from money out (expenses and purchases). Within those, group transactions in a way that maps to your accounting, for example:

• Sales / income — customer payments and deposits for your taxable sales
• Purchases / expenses — supplier payments, premises costs, equipment, and other business outgoings
• Refunds — handle these per transaction rather than as a single bucket (see below)
• Transfers and personal items — owner drawings, transfers between accounts, loan movements

Refunds need transaction-specific treatment because their tax effect depends on what they reverse. A refund you give a customer reverses a sale, so it reduces your sales and the GST you collected — it is not a purchase. A refund you receive from a supplier reverses a purchase, so it reduces your purchases and any GST credit you had claimed — it is not income. Do not lump refunds in with sales or income; trace each one back to the original transaction and apply the opposite GST effect.

The transfers group matters too: transfers and personal spending are not business sales or expenses and must not be counted in your GST figures. Filtering them out early prevents inflated totals later.

At this stage you are only sorting transactions, not deciding GST. Whether a purchase carries a GST credit is worked out per transaction in the next step, not assumed from its category.

Step 3: Identify the GST components

This is the step that turns categorized transactions into BAS figures. GST in Australia is generally 10%, but not every transaction includes it. You need to work out the GST portion of your sales (GST collected) and the GST portion of your purchases (GST credits you can claim).

GST credits are not automatic. Per ATO guidance, a purchase only gives you a credit when it is for your business use (not private use), the supply actually included GST in the price, and you hold a valid tax invoice for it. Some supplies are GST-free or input-taxed — for example certain food, some health and education services, and most bank fees — and carry no GST to claim. So check each purchase against those conditions rather than assuming any category of expense automatically contains claimable GST; if any condition is not met, that row has no GST credit.

The same per-transaction care applies to sales: work out whether each one is taxable, GST-free, or input-taxed before counting its GST. The ATO publishes guidance on which sales and purchases include GST and on the records you need; check it at the official site, ato.gov.au, if you are unsure how a particular transaction is treated.

For a tax-inclusive amount, the GST component is the total divided by 11. Add a column in your spreadsheet that calculates this only for the rows you have flagged as GST-applicable, and leave it blank for GST-free, input-taxed, and out-of-scope rows. Summing that column gives you the GST on sales and, separately, the GST on purchases.

Step 4: Reconcile against your records

Bank statement data is only reliable if it is complete and matches reality. Before trusting your totals, reconcile them against your other records:

• Compare sales in the bank feed with your invoices and sales receipts. Add any cash sales or payments collected through a separate processor that did not hit this bank account in the period.
• Check expense totals against supplier invoices and receipts, so you are claiming GST credits you actually hold a valid tax invoice for.
• Confirm the closing balance on the spreadsheet matches the closing balance printed on the statement. A mismatch means a row was dropped or duplicated during conversion.

Accuracy here depends entirely on having complete records. If invoices or receipts are missing, the bank statement alone cannot tell you the correct GST treatment, and your BAS figures will be estimates rather than facts.

Step 5: Transfer the figures to the BAS

With reconciled totals in hand, you can populate the BAS. The figures you have built map to the common GST labels: total sales, GST on sales, and GST on purchases. The exact labels and the method you use depend on whether you report on the full or simpler GST method and on your registration details, so follow the field-by-field walkthrough in our guide to how to do a BAS statement.

Keep the spreadsheet, the converted statements, and the supporting invoices together. The ATO expects you to retain records that support the figures you report, and a tidy workbook makes the next BAS — and any later review — far quicker.

What the bank statement cannot do for you

It is worth repeating where this workflow stops. The bank feed shows money that moved through the account; it does not interpret the tax treatment for you, and it cannot include activity that never touched the account. The judgement calls — is this sale GST-free, is this a valid tax invoice, is this transaction even business-related — still rest on your records and, where needed, professional advice.

Used with that caveat in mind, starting from bank statement data gives you a structured, repeatable way to assemble most of your BAS figures. Convert, categorize, identify the GST, reconcile, and transfer — then check the detail against the ATO's own guidance at ato.gov.au before you lodge.