The example being we are selling tickets (which include GST) for a future event.  From my reading the double entries are 1) Credit Bank Account, 2) Debit Unearned Revenue.  When the event is happend I can then credit Unearned Revenue and Debit Earned Revenue. 

The question I have is when would GST be liable given I collect GST upfront but only recognise the revenue later on.   Also keeping in mind that there is the ability to cancel tickets (albeit with the loss of a % of the ticket).