What is the difference between Simpler BAS and Full BAS?

Simpler BAS (default for businesses with turnover under $10 million) requires only 3 GST labels: G1 (total sales), 1A (GST on sales), and 1B (GST on purchases). Full BAS requires all G1–G20 labels for detailed reporting.

When can I lodge monthly instead of quarterly?

Monthly BAS is required if your GST turnover is $20 million or more. Voluntary monthly lodging is available if you regularly receive GST refunds. Apply to the ATO to change your reporting cycle.

What happens if I lodge my BAS late?

The ATO charges a Failure to Lodge (FTL) penalty of one penalty unit ($313 for 2025–26) for each 28-day period the BAS is overdue, up to a maximum of 5 penalty units ($1,565). Interest also applies on unpaid amounts (General Interest Charge).

Can I amend a BAS after lodging?

Yes. Lodge a revised BAS through the Business Portal or your tax agent. Amendments within 4 years are generally accepted. For older periods, contact the ATO directly.

Do I need to lodge a BAS if I had no activity?

Yes — you must lodge a 'nil' BAS even if you had no sales or purchases. Failing to lodge nil returns attracts the same FTL penalties as regular returns.

← Back to Australia Tax Guide

BAS Guide

BAS Lodgement Step-by-Step Guide

Complete guide to lodging your Business Activity Statement (BAS) with the ATO. GST labels G1–G20 explained, PAYG withholding, due dates, and Simpler BAS vs Full BAS.

How to Lodge Your BAS — 7 Steps

From ATO login to payment — complete walkthrough.

Log in to ATO Business Portal or myGov

Use your myGovID (Relationship Authorisation Manager for businesses) or log in through your registered tax agent's software. Sole traders can use their personal myGov linked to ATO.

Select your BAS period

Choose the correct reporting period — quarterly (most common) or monthly. The ATO pre-fills some amounts if you've linked bank feeds. Verify pre-filled data before proceeding.

Report GST (Labels G1–G20)

Enter your sales and purchase figures. If using Simpler BAS (turnover < $10 million), you only need G1 (total sales), 1A (GST collected), and 1B (GST paid). Full BAS requires all G1–G20 labels.

Report PAYG Withholding (Labels W1–W5)

W1 = Total salary/wages and other payments. W2 = Amounts withheld from payments (tax withheld from employees). W3 = Withheld from investment distributions. W4 = Withheld where no ABN quoted.

Report PAYG Instalments (Label T7–T9)

If you pay tax by instalments, enter your instalment amount (T7) or calculate from your instalment rate × instalment income. T8 = Estimated net tax for the year. T9 = Varied amount.

Review & Lodge

Review the summary showing net GST (1A – 1B), PAYG withholding (W2+W3+W4), and PAYG instalments. The total amount owing or refundable is calculated. Submit electronically via the portal.

Pay or Receive Refund

If you owe, pay by the due date via BPAY, direct debit, or credit card. Refunds are typically processed within 14 days for electronic lodgement. Payment plans available if you can't pay in full.

BAS GST Labels — G1 to G20 Explained

Full BAS requires these labels. Simpler BAS only needs G1, 1A, and 1B.

Label	Description	Notes
G1	Total sales (including GST)	All taxable sales, GST-free sales, and input-taxed sales
G2	Export sales	GST-free exports — goods shipped overseas
G3	Other GST-free sales	Food, medical, education, exports of services
G4	Input taxed sales	Financial supplies, residential rent
G5	G2 + G3 + G4 total	Auto-calculated: sum of non-taxable sales
G6	Total sales subject to GST (G1 – G5)	Net taxable sales used to calculate GST collected
G7	Adjustments	Bad debts recovered, change of use, other adjustments
G8	Total GST on sales (G6 ÷ 11 + G7)	GST you collected from customers
G9	Total GST on sales	Carried forward to calculate net GST position
G10	Capital purchases (including GST)	Equipment, vehicles, plant over $1,000
G11	Non-capital purchases (including GST)	All other business purchases including GST
G12	G10 + G11 total	Auto-calculated: total purchases
G13	Purchases for making input taxed sales	Purchases related to financial supplies or residential rent
G14	Purchases without GST in the price	Wages, GST-free purchases, private purchases
G15	Estimated purchases for private use	Business portion of mixed-use purchases
G16	G13 + G14 + G15 total	Auto-calculated: non-creditable purchases
G17	Total purchases subject to GST (G12 – G16)	Net purchases eligible for GST credit
G18	Adjustments	Bad debts written off, change of use adjustments
G19	Total GST on purchases (G17 ÷ 11 + G18)	GST you paid on business purchases
G20	Total GST on purchases	Your input tax credits

Quarterly BAS Due Dates — 2026

Standard quarterly lodgement schedule. Monthly lodgers must submit by the 21st of the following month.

Quarter	Due Date
July – September (Q1)	28 October
October – December (Q2)	28 February
January – March (Q3)	28 April
April – June (Q4)	28 July

Frequently Asked Questions

← Australia Tax Overview STP Reporting Guide