Welcome to the Community. I'm here to help you with your concern related to running a report in QuickBooks Online.
There are multiple GST reports you can use to show GST related to your sales and purchases. I suggest running the GSTR 9 report to gather the necessary information.
This is the annual summary of your sales, purchases, and taxes recorded in the books. Please follow these steps to run the report:
On the left navigation bar, click Reports.
Scroll down to GST returns, then choose GSTR 9.
Press Generate GSTR 9.
Currently, a direct way to customize the report is unavailable. I recommend extracting the GSTR 9 report and download it in excel format. You should see an option to download after generating the report.
You can use the following articles to view the complete list of GST reports, as well as the specific tables in GSTR9 that needs to be filled out manually in QuickBooks: