I can help share some insights concerning exporting invoices in Quickbooks Online. If you're referring to export your invoice to Excel, you can follow the steps below:
Go to the Reports tab.
Enter the Invoice list in the search box, then enter.
Customized the Report period and hit Run report.
In the reports page, click the Export button then select Export to Excel.
For more information about importing or exporting data, you can check out these articles:
It's my priority to help you with exporting your invoices accordingly, @Ashish Tulsian.
As per section 16 of the IGST Act, 2017, the export of goods and services is treated as a zero-rated supply. This means that the GST would not apply to the export of any kind of goods or services. Since selecting the GST 0% saves the payment of GST, you need to choose the GST exempt option.
To learn more about the zero-rated supplies and Letter of Undertaking, you can check out these links: