My domain expired and stopped working - can I get it back?

Usually yes, if you act quickly - an expired .au domain does not vanish immediately but moves through a grace period before it is released back to the public. The sooner you renew, the simpler and cheaper it is:

• The grace window - for a short period after expiry you can still renew at the normal price; your site and email are down, but the domain is yours to recover.
• The risk after that - once the grace period ends the domain is released and anyone can register it, including someone who targets lapsed business names.
• Act through your registrar - log in and renew immediately; if you cannot get in, contact the registrar directly rather than waiting.

Renew the moment you notice, and turn on auto-renewal so a missed invoice can never take your domain offline again.