A Director Penalty Notice is the ATO’s way of holding you personally liable for...

https://dlf-ne.org/dpn-postal-delay-the-21-day-trap-that-could-cost-you-your-personal-assets/

A Director Penalty Notice is the ATO’s way of holding you personally liable for company PAYG, GST, and SGC debts. The 21-day clock starts the moment it is issued, so do not ignore it