Tax rule Australia

BAS quarters: when your GST periods start and end

How often you report GST on your BAS, as the ATO sets it out, and the quarters Bilbx's Tax Lab shows: quarters ending September, December, March and June.

The periods Tax Lab starts with

Quarters ending September, December, March and June

Checked against the ATO's own pages on . This is the figure Bilbx uses.

The rule

  1. You must lodge your BAS quarterly if your GST turnover is less than $20 million and the ATO has not told you to report monthly.

    What the ATO says

    “You must lodge your BAS quarterly if your GST turnover is less than $20 million and we haven't told you that you must report monthly.”

  2. Quarter 1 is July, August and September; quarter 2 is October, November and December; quarter 3 is January, February and March; quarter 4 is April, May and June.

    What the ATO says

    “1. July, August and September”

    “2. October, November and December”

    “3. January, February and March”

    “4. April, May and June”

  3. You can choose to report monthly if your GST turnover is less than $20 million.

    What the ATO says

    “You can choose to report monthly if your GST turnover is less than $20 million.”

  4. You lodge your BAS annually if you are voluntarily registered for GST and your GST turnover is under $75,000.

    What the ATO says

    “You lodge your BAS annually if both of the following apply”

    “you are voluntarily registered for GST”

    “your GST turnover is under $75,000”

How Bilbx applies it

  • Tax Lab, part of Bilbx Premium, shows your GST for each filing period, and starts with quarters ending September, December, March and June.
  • It numbers the quarters from July, as the ATO does.
  • In Settings you can choose monthly, every two, three or six months, or yearly, and the month a period ends in.

Worked examples

Bilbx's own tests run these exact cases against the website and the app.

  • 15 August 2026

    Filing:
    Quarterly, ending Mar, Jun, Sep, Dec
    Tax Lab's period:
    Q1: 1 July 2026 to 30 September 2026

  • 1 October 2026

    Filing:
    Quarterly, ending Mar, Jun, Sep, Dec
    Tax Lab's period:
    Q2: 1 October 2026 to 31 December 2026

  • 31 March 2027

    Filing:
    Quarterly, ending Mar, Jun, Sep, Dec
    Tax Lab's period:
    Q3: 1 January 2027 to 31 March 2027

  • 30 June 2027

    Filing:
    Quarterly, ending Mar, Jun, Sep, Dec
    Tax Lab's period:
    Q4: 1 April 2027 to 30 June 2027

  • 10 February 2026

    Filing:
    Monthly
    Tax Lab's period:
    1 February 2026 to 28 February 2026

  • 1 July 2026

    Filing:
    Yearly, ending Jun
    Tax Lab's period:
    1 July 2026 to 30 June 2027

Check a receipt

Enter a receipt to see what Bilbx does with it under Australia's rules. It is worked out in your browser by the same code the app runs, and nothing you enter is sent or stored.

Enter a date and a total to see the answers.

Sources

Spotted something that doesn't match the ATO's guidance?

Every sentence in the rule is checked against the ATO's own guidance, quoted beneath it and linked above. Last checked . Rules version 60f9162250af. Terms.

More for Australia: every tax rule Bilbx applies and guides on receipts and tax records.