BAS Preparation Checklist

Most BAS stress comes from doing the quarter's bookkeeping and the BAS on the same afternoon. Lodging from a cold start means every question — was that big deposit income, did the feed import everything, why is the refund so large — gets asked at the worst possible moment. A short checklist, run before you look at the BAS itself, turns lodgement day into the easiest part of the quarter.

Start with the bank, not the BAS

• Reconcile every account to the end of the quarter — business bank accounts, credit cards and any loan account with GST-relevant activity.
• Check the statement balance, not just the empty coding queue. Compare the balance in Xero or MYOB to the actual bank statement at quarter end; this is what catches dropped or duplicated feed lines.
• Empty the suspense account. Anything you could not identify during the quarter needs an answer now, not a guess.

Review the GST coding

• Spot-check the largest and oddest transactions. Open the GST detail report and scan for anything unusual — big amounts, new suppliers, and anything claiming full GST that should not be.
• Look for the no-GST traps. Bank fees, interest and many government charges carry no GST credit even though money left the account.
• Remove private spending. Personal purchases on the business card belong to drawings or the loan account, not to expenses with a GST credit attached — and part-private items, like a vehicle, should only claim the business portion.

Tie wages to payroll, not to memory

If you employ staff, W1 and W2 on the BAS should agree with your payroll reports for the same period — W1 with gross wages and W2 with the tax withheld. If the BAS and the payroll report disagree, one of them is wrong, and the ATO can already see the payroll side through Single Touch Payroll. Reconcile the difference before lodging, not after the mismatch letter arrives.

Check the other labels

If a PAYG instalment appears on your BAS, check it against how the year is actually tracking before paying it on autopilot. Instalments can be varied, but a variation that turns out too low can attract interest, so vary conservatively and on evidence rather than optimism. Then give the whole form a common-sense read: does the GST on sales roughly fit the quarter you actually had?

Know your dates

Quarterly BAS due dates generally fall on the 28th of the month after quarter end — 28th October, 28th February, 28th April and 28th July — but check the current ATO dates for your own cycle. Lodging through a registered agent often comes with extra time for most quarters; confirm your actual due date with your agent rather than assuming it.

What we commonly see go wrong

• Lodging straight from the software's GST report without the statement-balance check, on a quarter where the feed dropped lines.
• GST credits claimed on bank fees, interest, wages and superannuation — none of which carry GST.
• W1 and W2 typed from memory and drifting away from the payroll reports the ATO already holds.
• A duplicated supplier bill quietly inflating both expenses and the GST refund.
• The same coding error repeating for four quarters because nobody reviewed the pattern the software had learned.

A worked example

As an illustration: a builder's BAS shows an unusually large refund. The pre-lodgement review finds two causes — a supplier bill entered twice, once from the emailed invoice and once from the bank feed, and materials for a private renovation coded to the business with full GST credits. Caught before lodgement, both are ten-minute fixes. Lodged and later reviewed, the same two items become an amendment, a repayment, and a conversation with the ATO that extends to every other line in the file.

When to get help

If the checklist keeps surfacing the same problems, if the file is more than a quarter behind, or if you are lodging figures you could not confidently explain in a review, it is usually cheaper to have the process fixed once than to keep lodging on hope. A BAS built on a reconciled file is a boring document — which is exactly what it should be.

When is my quarterly BAS due?

Generally on the 28th of the month after quarter end — 28th October, 28th February, 28th April and 28th July — though your cycle may differ, so check the current ATO dates. Lodging through a registered agent often provides extra time for most quarters; confirm your date rather than assuming it.

What if I find a mistake after the BAS is lodged?

Many GST errors can be corrected on a later BAS within limits the ATO sets, and others need a formal amendment. Either way, fix it deliberately rather than hoping it washes out — corrections made voluntarily are generally treated more favourably than ones found in a review.

Do wages and super have GST on them?

No. Wages are reported at W1 and the withholding at W2, but neither carries GST, and neither does superannuation. Claiming GST credits on payroll amounts is one of the most common BAS errors we see.