Hi there, @sales216.

You'll have to create a GST again then make sure to select the IGST tax once you create an invoice. Let me walk you through the steps on how to create IGST tax. Here's how:

1. From the left panel, go to the Taxes menu.
2. Click the Add tax button.
3. Select the Tax rate section.
4. Enter the tax name.
5. Fill out the description. (Optional)
6. In the Tax agency dropdown, choose the GST option. Then, put a checkmark in the Sales box.
7. Enter all the information needed in the fields.
8. Choose Output - GST in the Show tax amount on return line dropdown arrow.
9. Once done, hit the Save button.

I've also added an article on how to apply IGST to your invoice.

If you have additional questions, please don't hesitate to leave a message in the comment section. I'll be happier to help. Take care, and have a good day.