If you have some queries about your GST and you want to check it, why it does not seem to be right, what you can do is audit the figures on a daily, weekly, monthly or whatever is required to try to find where the error.
You will find it in here
Cash register> Register reports > Sales > GST Summary for a given period
This is an extremely detailed report showing the GST information based on the selected period.
What I find it particularly useful is in tracking down errors. For example, say I see a GST figure in the BAS that looks off. Using this report I can break it down to two sections of one and a half months each, then see which one looks wrong. Then I take that one that looks wrong and split it into two sections, check them and so on till I find the day of the error.
Give it a shot and see how you go.
Also, there are many other reports there too to help our clients do better.