BAS Due Dates 2025-26 and What a Registered BAS Agent Does

Missing a Business Activity Statement deadline costs more than most business owners realise. From 1 July 2025, the ATO's failure to lodge penalty is $330 per 28-day period, and it compounds automatically on every BAS you have not lodged, not just the most recent one. Interest charges accrue immediately on any unpaid amount at 10.96% per annum, compounded daily.

This guide covers every BAS due date for the 2025-26 financial year for quarterly, monthly, and annual reporters, including the extended deadlines available when you lodge through a registered BAS or tax agent. It also explains what a registered BAS agent actually does, how they differ from an unregistered bookkeeper, and why the distinction matters for your business.

Yes, The Kalculators are registered BAS agents as well as registered tax agents. Both registrations are held under the Tax Agent Services Act 2009 and regulated by the Tax Practitioners Board (TPB).

What Is a Business Activity Statement (BAS)?

A Business Activity Statement is a form submitted to the ATO that reports your business tax obligations for a specific period. If your business is registered for GST, you are required to lodge a BAS. Most businesses lodge quarterly. Businesses with a GST turnover of $20 million or more must lodge monthly.

A standard BAS can include:

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  GST: the GST collected on your sales (output tax) minus the GST you paid on business purchases (input tax credits). If you collected more than you paid, you owe the ATO the difference. If you paid more than you collected, the ATO owes you a refund.
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  PAYG withholding: the income tax you have withheld from employee wages and remitted to the ATO on their behalf.
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  PAYG instalments: prepayments of your own income tax (for sole traders, company directors, and other individuals with business income above ATO thresholds).
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  FBT instalments: quarterly prepayments of Fringe Benefits Tax if your business provides fringe benefits to employees.
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  Wine Equalisation Tax (WET) and Luxury Car Tax (LCT): for businesses operating in those specific sectors.

Not all sections apply to every business. A sole trader with no employees and no FBT obligations may only be reporting GST and PAYG instalments. A company with 20 staff in a fully maintained vehicle fleet will have additional sections. Your small business accounting requirements determine which parts of the BAS apply to you.

Who Needs to Lodge a BAS?

You are required to lodge a BAS if your business is registered for GST. You must register for GST if your annual GST turnover is $75,000 or more (or $150,000 or more for not-for-profit bodies). Businesses below this threshold can voluntarily register for GST and must also lodge a BAS.

Sole traders, companies, trusts, and partnerships can all be required to lodge a BAS. New businesses that expect to reach the GST threshold should register before crossing it, not after.

BAS Due Dates 2025-26: Every Deadline in One Place

Quarterly BAS Due Dates (Most Common for Australian SMEs)

Most Australian small and medium businesses lodge their quarterly returns. The four quarters align with the Australian financial year, and each BAS covers a three-month period. Businesses lodging through a registered BAS agent or tax agent receive extended deadlines for Q1, Q3, and Q4 under the ATO's BAS Agent Lodgment Program. Q2 is the exception: the deadline is the same for everyone.

Important: the Q2 extension trap. Many business owners assume their BAS agent will automatically get them more time for every quarter. The October to December quarter (Q2) has no extension and is always due 28 February, regardless of whether you lodge through an agent. Missing this deadline is more common than in any other quarter.

If a due date falls on a weekend or public holiday, the ATO automatically moves it to the next business day. All dates above are the standard ATO deadlines. Check ato.gov.au for any adjustments due to weekends or public holidays in your state.

Monthly BAS Due Dates 2025-26

Businesses with a GST turnover of $20 million or more are required to lodge monthly. Businesses below this threshold can elect to lodge monthly (which has the advantage of receiving GST refunds more frequently). Monthly BAS must be lodged by the 21st of the following month. There is no agent extension for monthly lodgments.

Annual BAS Due Date

Businesses with a GST turnover below the registration threshold that have voluntarily registered for GST may be eligible to lodge annually. The annual BAS for the 2025-26 financial year is due by 31 October 2026 (or at the same time as the income tax return if an agent lodges the tax return under the tax agent lodgment program).

What Happens When You Miss a BAS Deadline

The ATO has two separate penalties that both apply when you miss a deadline and do not pay. Most businesses that fall into difficulty face both.

Failure to Lodge (FTL) penalty: calculated in penalty units, each worth $330 from 1 July 2025. One penalty unit applies per 28-day period the BAS is overdue, up to a maximum of five units for small entities.

What Is a Registered BAS Agent?

A registered BAS agent is a professional who is licensed by the Tax Practitioners Board (TPB) to provide BAS services to clients for a fee. BAS agents operate under the Tax Agent Services Act 2009 and must meet strict educational, experience, and continuing professional education requirements to maintain their registration.

Registration is not optional for anyone who prepares or lodges BAS documents on behalf of clients for payment. An unregistered person who prepares and lodges a client's BAS for a fee is operating illegally, regardless of their experience or competence. You can verify any individual's or firm's registration status on the Tax Practitioners Board register at tpb.gov.au.

What a Registered BAS Agent Can Do

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  Prepare and lodge your BAS and other related forms on your behalf
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  Represent you before the ATO in relation to BAS matters
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  Access the BAS agent lodgment program for extended deadlines on Q1, Q3, and Q4
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  Advise on GST obligations, input tax credit entitlements, and BAS-related compliance
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  Handle PAYG withholding calculations and reconciliations
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  Correspond with the ATO on your behalf for BAS-related matters

What a Registered BAS Agent Cannot Do

A BAS agent (as distinct from a tax agent) is not authorised to prepare or lodge income tax returns, or provide advice on income tax matters beyond what is directly connected to the BAS. If your adviser handles both your BAS and your income tax return, they must hold a tax agent registration (which also covers BAS services). The Kalculators hold both registrations.

BAS Agent vs Tax Agent: What Is the Difference?

The key distinction tax agents are licensed to provide a broader range of services, including income tax returns, tax planning, and full ATO representation. BAS agents are specifically licensed for BAS and GST-related services. In practice, most registered tax agents are also authorised to provide BAS services, but the reverse is not true.

What The Kalculators Do as Your Registered BAS Agent

Our registered BAS agents and tax agents work with small business bookkeeping clients across Adelaide and online.

When you outsource your BAS to us, here is what we handle:

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  Transaction coding: We code all your business transactions in Xero, MYOB, QuickBooks, or Reckon to meet management reporting, statutory, and general ledger requirements.
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  GST reconciliation: We reconcile the GST on all your sales and purchases, identify input tax credit entitlements, and calculate the net amount owing or refundable.
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  PAYG withholding: We calculate and reconcile PAYG withholding from your employee wages and include it correctly in your BAS.
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  P&L and balance sheet reconciliation: We ensure your profit and loss statement and balance sheet reconcile before lodging, so your BAS figures match your books.
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  ATO lodgment: We lodge the BAS electronically on your behalf and provide you with an extension under the BAS agent lodgment program for Q1, Q3, and Q4, giving you up to 28 extra days on those quarters.
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  ATO correspondence: We deal with the ATO on your behalf for any queries or disputes relating to your BAS obligations.

We also provide outsourced payroll services and sole trader BAS lodgment for self-employed Australians who need regular, reliable compliance support.

How to Verify That Your Bookkeeper or BAS Agent Is Registered

Before engaging anyone to prepare your BAS for payment, verify their registration on the TPB register at tpb.gov.au/registered-tax-practitioners. Search by name or ABN. A registered BAS agent or tax agent will appear with their registration number, registration type, and registration expiry date.

If someone is not on the register but is charging you to prepare your BAS, they are operating outside the law. You also lose the protection of the TPB professional standards framework if something goes wrong.

How The Kalculators Can Help With Your BAS

Whether you are a sole trader managing your own GST obligations, a small business with staff and quarterly PAYG commitments, or a company needing full-service business bookkeeping and BAS lodgment, our registered BAS agents and tax agents handle the full cycle.

We take BAS compliance seriously because missing deadlines has real financial consequences. Our clients receive a checklist of required inputs before each BAS period, and we lodge early enough to give you the agent extension benefit on every eligible quarter.

Call (08) 7480 2593, Monday to Friday, 9:00 AM to 6:00 PM, or visit our offices at 182 Salisbury Highway, Salisbury; 315 Prospect Road, Blair Athol; or 280 Main South Road, Morphett Vale. Online BAS services are also available for clients in Murray Bridge, Woodville, Melrose Park, Port Augusta, Prospect, and Brighton via info@thekalculators.com.au.