BAS Lodgement, Step by Step

The BAS is a reporting form, not a calculation you do at the end of a quarter. Everything on it is a summary of transactions that were coded when they happened. If the coding was consistent, preparing the statement is largely mechanical. If it was not, the statement becomes an exercise in finding out what actually went on in the ledger.

That is the single most useful thing to understand about BAS: the work is in the bookkeeping, not the form.

How often a BAS is lodged

Reporting cycles differ between businesses. Quarterly is the most common, but monthly applies in some cases and annual reporting is available to others. Which cycle applies depends on turnover and on registration choices, and the ATO sets and publishes the due dates for each.

Businesses that lodge through a registered agent may have different dates from those lodging directly. It is worth knowing which cycle and which dates apply to you specifically rather than assuming the common case.

What actually goes on the statement

Depending on registrations, a BAS can report several obligations on one form:

• GST collected on sales and GST paid on purchases, netted to an amount payable or refundable.
• PAYG withholding - tax withheld from employee wages and from certain payments to contractors.
• PAYG instalments - prepayments toward the income tax liability for the year.
• Other obligations such as fuel tax credits or wine equalisation tax, where they apply.

Not every business reports every item. The form you receive reflects your registrations, which is why comparing your BAS to somebody else’s is rarely useful.

Reconciling before you lodge

The step most often skipped is the simplest. Before a statement goes anywhere, the GST control accounts in the ledger should agree with what the statement says, and the wages figure should agree with what was reported through Single Touch Payroll. Where they do not, the difference is telling you something — usually that a transaction was coded to the wrong account, or that a payroll run was processed outside the accounting file.

Chasing that difference before lodgement takes minutes. Chasing it eighteen months later, when the ATO raises it against three separate quarters, takes considerably longer and starts from a worse position.

The other pre-lodgement check worth doing is a comparison against prior periods. A GST refund in a business that normally pays, or a sudden halving of reported wages, is not necessarily wrong — but it is worth understanding before it is lodged rather than after it is queried.

Where the errors usually are

In practice, most amendments trace back to a handful of recurring coding problems. Purchases that carry no GST — certain financial supplies, some government charges, genuine GST-free items — coded as though they did. Capital purchases treated as ordinary expenses. Personal transactions run through the business account and never separated out. Wages posted in a way that does not agree with what was reported through Single Touch Payroll.

Each of these is small in isolation and cumulative in effect. The fix is not a better BAS process; it is consistent coding through the quarter, which is the ongoing work described under bookkeeping and financial reporting. Where wages are involved, the reporting has to agree with what was lodged under payroll and STP.

If a lodged BAS turns out to be wrong

Errors happen, and there is a defined path for correcting them. Depending on the size and nature of the error, some corrections can be made on a later statement while others require a revision to the original. The ATO publishes the rules that determine which applies.

What matters more is the pattern. A single miscoded invoice is a correction. The same category miscoded every quarter for two years is a bookkeeping problem, and correcting the statements without fixing the coding just means doing it again next quarter.