These dates are from the ATO website and do not take into account possible extensions.

See ATO Due dates by month to check monthly lodgment and payment dates.

BAS/IAS Monthly Lodgements
Final dates for lodgements and payments:

July Activity Statement: 21 August 2021

August Activity Statement: 21 September 2021

BAS Quarterly Lodgements
Final dates for lodgements and payments:

4th Quarter 2021 Financial Year:
June Quarter 2021 (incl. PAYGI)
28 July, 2021

1st Quarter 2022 Financial Year:
September Quarter 2021 (incl. PAYGI)
28 October, 2021

When a due date falls on a Saturday, Sunday or Public Holiday*, you can lodge or pay on the next business day.

*A day that is a public holiday for the whole of any state or territory in Australia.

Due date for super guarantee contributions:

4th Quarter 2021 Financial Year:
April to June 2021 – contributions must be in the fund by 28 July, 2021

1st Quarter 2022 Financial Year:
July to September 2021 – contributions must be in the fund by 28 October, 2021

Late payments of superannuation are not tax deductible.

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Source: The ICB Newsletter, Vol 13 Issue 2, August 2021