If you have gone live onto Xero in the middle of a BAS reporting period you will need to pull data from both NetSuite and Xero. Then add the amounts together to lodge the BAS.
Before Xero Conversion date:
In NetSuite you can use your navigation shortcut menu to access the related GST Summary reports or click on the relevant link below:
From Conversion date:
The Xero Activity Statement report can be found by navigating to Accounting > Reports > Scroll down to Taxes & Balances > select activity statement