The first thing you need to answer this question is to know who will be responding when your beacon goes off. The beacon manufacturer should be able to provide you with this information. Then you can find out what their policies are in regards to false alarms. The responsder may vary depending on where you are traveling. Often, the very first response is to contact an emergency contact phone number you provide when you register the unit, to find out whether it is a false alarm or not. In this case, you tell them it was an accident, and the case is closed with no more trouble.
But if you do set it off accidently, and know that it happened, your best option is to make sure everyone knows it was an accident as quickly as possible. If it happens at home, immediately contact the responders, and let them know what happened.
If it happens somewhere remote, you may still be able to call and let them know what’s happened. If you can’t, stay put until the rescuers come. You’ll need to apologize, and depending on their policies, maybe pay for their time and expense. But by staying in your last known location, you will have minimized their time and trouble to reach you. You may be facing fines and rescue costs for a false alarm, but at least you minimized the rescue costs. Also, a lot of agencies won’t fine you for an accident, because they don’t want to discourage people from carrying beacons.
If it happens somewhere remote, and you don’t know that it’s happened, your rescuers will be relying on the plans you left before heading out (you did leave detailed written plans, right?). This will still let them find you fairly easily because they know where you expect to be. In either of these two cases, some agencies will charge you for the rescue, some won’t. If no one knows where you might be, except for a last known point, and a rescue has to start a serious search, it could get expensive, and a lot more groups will charge you because their expense was high, and you failed to follow the good practices that would help them minimize the cost (not setting off the beacon in the first place, and not letting someone at home know where you were going).
All the models I’ve seen are very hard to set off accidentally, and if you store it and pack it with reasonably care, it won’t happen.
My experience is in the US. Rescue policy is determined very regionally, often on a park by park, or at most state by state basis. I’ve got no idea how it would be handled in Australia.