Unregistered airports?
 

I found an airport, namely Charlton Airport in VIC (https://goo.gl/maps/ahY9RtX2wq32), that I cannot find in the ERSA.
Where can I find more information about this airport (landing fees, circuits, etc.)? It's more of a single runway really.

And is there an official register with all airports in Australia? I thought that familiarizing myself with the AIP documents would provide all information I'd ever need.

Ah, here's another one: Quambatook (https://goo.gl/maps/j4tQSFsw7862).

The DAH has every certified and uncertified aerodrome in Australia that are currently listed in the ERSA FAC directory, in Section 17 and 18. The ERSA Encode/Decode tables show Charlton in there, but with no other data, or details of who to contact.

Phone the shire council and ask them

HERE

The Vic and Tas Country Airstrip Guide has information about both Charlton and Quambatook airstrips.
VIC / TAS Country Airstrip Guide

The strips you named are marked as strips on my EFB charts.

There are two airstrips at Quakbatook. Both are PPR but the more useful is just 500 metres from the town.

Kaz

There are probably twice as many strips in Aus than what's documented. Be good to have a national database..
Country Airstrips Guides used to be all there was, remember the days you carried books around for this stuff?
Quite like the Country Airstrips Australia site. It's a free site offering more than just strip info, but local knowledge of where to stay, what to do, how to get into town etc.

Point taken, however Country Airstrips Guide is available in electronic format on some EFBs.