BAS Preparation Checklist for Perth Small Businesses

General information only. This article does not constitute financial, tax or legal advice. BAS preparation and lodgement must be carried out by a registered BAS Agent or tax agent if you are paying for that service. Please consult a registered professional for advice specific to your business.

If you run a GST-registered business in Perth, your Business Activity Statement (BAS) is due quarterly — or monthly if you've opted in. Missing the deadline or lodging with errors can result in penalties and interest charges from the ATO.

The good news is that BAS preparation doesn't have to be stressful. With a clear checklist and clean bookkeeping records, the process is straightforward.

Here's a practical BAS preparation checklist for Perth small businesses.

What Is a BAS?

A Business Activity Statement (BAS) is a form you submit to the ATO to report and pay your tax obligations. For most small businesses, the BAS includes:

GST — the difference between GST collected on sales and GST paid on purchases
PAYG withholding — tax withheld from employee wages
PAYG instalments — prepayments toward your own income tax (if applicable)
Other obligations — such as fuel tax credits or luxury car tax, if relevant

Before You Start: Get Your Records in Order

The most important step in BAS preparation is having clean, reconciled bookkeeping records. If your bank accounts aren't reconciled and your transactions aren't coded correctly, your BAS figures will be wrong.

Checklist: Records to Have Ready

All bank accounts reconciled for the BAS period
All credit card accounts reconciled
All sales invoices entered and matched to payments received
All supplier bills entered with correct GST treatment
Payroll finalised and STP submissions up to date
Any cash transactions entered
Petty cash reconciled (if applicable)

Step 1: Check Your GST Figures

Your BAS will show:

G1: Total sales — your total turnover for the period
1A: GST on sales — GST collected from customers
1B: GST on purchases — GST credits from your business expenses

Before accepting these figures, check:

Are all sales coded with the correct GST treatment (taxable, GST-free, or out of scope)?
Are all purchase transactions coded correctly?
Have any private or non-business expenses been excluded?
Are any transactions coded as GST-free that should have GST (or vice versa)?

Common GST mistakes include:

Claiming GST credits on expenses that don't include GST
Forgetting to apply GST to all taxable sales
Incorrectly treating mixed-use expenses

Step 2: Check Your PAYG Withholding

If you have employees, you'll need to report the PAYG withholding amount for the period — the tax you've withheld from employee wages and paid (or need to pay) to the ATO.

Payroll for the period is finalised
PAYG withholding amount matches your payroll records
STP (Single Touch Payroll) submissions are up to date

Step 3: Check for Any Adjustments

Sometimes you'll need to make adjustments to your BAS — for example, if you've issued a credit note, had a bad debt, or made an error in a previous BAS period.

Any credit notes or refunds issued during the period are recorded
Any bad debts written off are recorded correctly
Any prior period corrections are noted

Step 4: Review the Final BAS Figures

Before lodging, do a final sense-check:

Does the total sales figure look reasonable for the period?
Does the GST on sales figure equal approximately 1/11th of taxable sales?
Does the GST on purchases figure look reasonable?
Is the net GST payable (or refundable) what you expected?

If something looks unusual, investigate before lodging. It's much easier to correct an error before lodgement than after.

Step 5: Lodge and Pay on Time

BAS lodgement deadlines are set by the ATO. Missing the deadline can result in a Failure to Lodge (FTL) penalty.

If you use a registered BAS Agent, they may have an extended lodgement deadline — which is one of the practical benefits of working with a registered agent.

BAS lodged by the due date (or agent lodgement date)
Payment arranged if a net amount is owing

What If Your Books Are Behind?

If your bookkeeping isn't up to date, you won't be able to prepare an accurate BAS. In this case, catch-up bookkeeping is the first step — getting your records reconciled and coded correctly before the BAS can be prepared.

The further behind your books are, the more time catch-up work takes. It's worth addressing this before your next BAS deadline rather than after.

Should You Use a Registered BAS Agent?

A registered BAS Agent is authorised to prepare and lodge BAS on your behalf for a fee. They are registered with the Tax Practitioners Board (TPB) and must meet ongoing professional and educational requirements.

Using a registered BAS Agent gives you:

Confidence that your BAS is prepared correctly
Protection under the Tax Agent Services Act
Potential access to extended lodgement deadlines
Someone who can communicate with the ATO on your behalf

At The Perth Bookkeeper, Agnieszka Peszel is a registered BAS Agent (No. 262 458 37) who works with Perth small businesses to keep their records clean and their BAS lodged on time.

FAQ: BAS Preparation for Perth Small Businesses

When is my BAS due? Quarterly BAS lodgement deadlines are generally the 28th of the month following the end of each quarter. If you use a registered BAS Agent, you may have an extended deadline. Check the ATO website or ask your BAS Agent for your specific due dates.

What happens if I lodge my BAS late? The ATO may apply a Failure to Lodge (FTL) penalty for late lodgement. The penalty amount depends on the size of your business and how late the lodgement is.

Can I prepare my own BAS? Yes — business owners can prepare and lodge their own BAS. However, if you pay someone else to prepare or lodge your BAS, that person must be a registered BAS Agent or tax agent.

What if I made an error on a previous BAS? Errors can usually be corrected on a future BAS or by contacting the ATO. A registered BAS Agent can advise on the best approach.

What is the difference between GST-free and out of scope? GST-free supplies are taxable supplies with a zero GST rate (such as most fresh food and some medical services). Out of scope means the transaction is not subject to GST at all (such as wages or loan repayments). The distinction matters for your BAS figures.

Need help getting your BAS ready? Book a free consultation with The Perth Bookkeeper — a registered BAS Agent serving Perth small businesses.

Learn more: Catch-Up Bookkeeping Perth | Bookkeeping Services Perth

BAS Preparation Checklist for Perth Small Businesses