BAS Lodgement Checklist for Small Business Owners (2026)

What Is a BAS and Who Needs to Lodge One?

A Business Activity Statement (BAS) is a form submitted to the Australian Taxation Office (ATO) by businesses registered for GST. It reports your GST collected on sales, GST paid on purchases, PAYG withholding (if you have employees), and PAYG instalments (if applicable).

If your business has an annual turnover of $75,000 or more (or $150,000 for not-for-profits), you are required to register for GST and lodge a BAS. Some businesses below the threshold voluntarily register for GST to claim input tax credits.

Most small businesses lodge quarterly, though some lodge monthly or annually depending on their turnover and ATO requirements.

2026 BAS Lodgement Due Dates

Here are the key quarterly BAS due dates for 2026. If you lodge through a registered tax agent or BAS agent, you may receive extended deadlines.

Self-lodgers (no agent)

• Q3 (January to March 2026): Due 28 April 2026
• Q4 (April to June 2026): Due 28 July 2026
• Q1 (July to September 2026): Due 28 October 2026
• Q2 (October to December 2026): Due 28 February 2027

Lodging through a BAS or Tax Agent

Your agent will have their own lodgement programme with the ATO, which often provides an extra four weeks beyond the self-lodgement dates. Check with your agent for the exact date.

Important: If the due date falls on a weekend or public holiday, the deadline moves to the next business day.

Your Complete BAS Lodgement Checklist

Use this checklist to prepare your BAS. Tick off each item before you submit.

1. Reconcile All Bank Accounts

This is the single most important step. Before you report any GST figures, make sure every transaction in the period is accounted for and reconciled in your accounting software.

• Reconcile all bank accounts, credit cards, and PayPal or Stripe accounts
• Clear any unreconciled items or investigate discrepancies
• Confirm your bank balance in Xero (or your accounting software) matches the actual bank statement balance

2. Review GST on All Transactions

Check that every transaction in the period has the correct GST treatment:

• GST on Income (10%): For standard taxable sales
• GST Free Income (0%): For GST-free items like most food, medical services, and exports
• GST on Expenses (10%): For business purchases that include GST
• BAS Excluded: For items like wages, superannuation, and bank transfers that sit outside the GST system

Common mistakes to look for:

• Personal expenses coded as business expenses
• Wages or super coded with GST (they should be BAS Excluded)
• International purchases coded with GST when they should be GST Free
• Petty cash or reimbursements missing GST treatment

3. Reconcile GST Control Accounts

If you are using Xero, run the GST Reconciliation Report (under Reports, then GST Reconciliation). This report compares the GST amounts on your BAS to the GST control account in your balance sheet. If they do not match, you have a problem that needs fixing before lodging.

4. Review Accounts Receivable and Accounts Payable

Outstanding invoices and bills can affect your BAS depending on whether you report GST on a cash basis or an accruals basis:

• Cash basis: You only report GST on transactions that have been received or paid during the quarter
• Accruals basis: You report GST on all invoices and bills raised during the quarter, regardless of whether payment has been received

Make sure you know which basis you are using and that your software is configured accordingly.

5. Check PAYG Withholding (If Applicable)

If you have employees, your BAS includes PAYG withholding, which is the tax you withhold from employee wages. Verify that:

• All pay runs for the quarter have been processed
• The PAYG withholding amount on the BAS matches the total tax withheld from payslips
• Any contractor payments that require withholding are included

6. Review PAYG Instalments (If Applicable)

If the ATO has issued you a PAYG instalment amount or rate, check that it appears correctly on your BAS. You can vary your instalment if your income has changed significantly, but be aware that under-estimating can result in penalties if the ATO determines the variation was unreasonable.

7. Run the BAS Report in Your Software

In Xero, go to Accounting, then Reports, then Activity Statement. Select the relevant period and review the pre-filled figures:

• 1A (GST on sales): Should match the GST collected on your taxable sales
• 1B (GST on purchases): Should match the GST paid on your business purchases
• W1 (Total salary/wages): Should match your payroll totals
• W2 (PAYG withheld): Should match the tax withheld from wages

Cross-check these figures against your profit and loss report and bank reconciliation. If something looks off, investigate before lodging.

8. Lodge the BAS

You can lodge your BAS through:

• The ATO's online services via myGov
• Your accounting software (Xero allows direct lodgement through the ATO's Standard Business Reporting channel)
• A registered BAS agent or tax agent

9. Pay the Amount Owing

If your BAS results in an amount owing (GST collected exceeds GST paid, plus any PAYG amounts), you must pay by the due date to avoid interest charges. Payment options include:

• BPAY using the details on your BAS
• Direct debit through the ATO portal
• Credit card (a surcharge may apply)

If you cannot pay the full amount, contact the ATO before the due date to arrange a payment plan. The ATO is generally cooperative if you reach out proactively rather than ignoring the bill.

What Happens If You Lodge Late?

The ATO can issue a Failure to Lodge (FTL) penalty for each 28-day period your BAS is overdue, up to a maximum of five periods. For small entities, the penalty is one penalty unit per period, which in 2026 is $330 per period (up to $1,650).

Beyond penalties, late lodgement can trigger ATO compliance activity, including audits. It also means your financial records are out of date, which makes it harder to manage cash flow and make informed business decisions.

How SortBooks Simplifies BAS Preparation

Preparing a BAS is largely about having clean, well-categorised data. That is exactly what SortBooks does. Our AI engine continuously reviews your Xero transactions, flags incorrect GST coding, catches duplicates, and ensures your books are BAS-ready before the quarter even ends.

Instead of a last-minute scramble to fix errors, you open your BAS report and the numbers are already clean. It is the difference between dreading BAS time and barely noticing it.

Final Thoughts

BAS lodgement is a non-negotiable part of running a GST-registered business in Australia. The good news is that with a solid process and clean books, it takes less time than most people think. Follow this checklist each quarter, stay on top of your reconciliation, and you will never have to stress about BAS again.