You can run the GST Summary and GST Details report in the GST center to see your GST and GST owed. Here's how:
Click on the GST tab.
Click on Run reports button.
Select either GST Summary or GST Details report.
Select a specific BAS period.
Click on Run report.
If you've lodged the BAS for a specific period, you can go to To Do, and click on the drop down arrow and click on BAS Summary or BAS Details report too.
From there you will see the figures of your GST sales, purchases and owed.
You can also check this article to learn more about GST:
You can run a report called GST Summary Report which can be access by going to Reports tab or GST tab and select Run reports. Then you can change the Report period according to your preference.