The TL;DR
The unofficial result for the Indigenous Voice to Parliament Referendum could be known on the night. However, if the votes are too close, it could take days to know the result. The official result will be declared later.
The counting process
The Australian Electoral Commission says an unofficial result for the referendum could be announced on the night of voting (14 October) depending on how close the count is.
If it is too close, it could take up to 13 days after polling for a result to be known.
On the night, every vote cast that day will be counted, as well as the large majority of votes cast at early voting centres. A small proportion of postal votes will be counted on the night.
The official result of the referendum
The AEC will not formally declare the result for the referendum on the night. They’re legally not allowed to — this is the same for federal elections.
They can only formally declare the official result when they are mathematically certain and the mandatory second count has taken place.
The process will be simpler than at federal elections because they do not need to count preferences.