When a Director Penalty Notice arrives, the 21-day clock starts immediately....

https://www.bookmark-maker.win/when-the-ato-sends-a-director-penalty-notice-that-21-day-clock-is

When a Director Penalty Notice arrives, the 21-day clock starts immediately. Ignoring it is risky because once that deadline passes, the ATO can pursue your personal assets for company tax debts like PAYG, GST, and SGC