Will GST default on AP Stand Alone Invoice if Purchasing module is not implemented?

Hi,

I am trying to understand the GST design from a tax defaulting perspective. How does the system determine the type of tax, IGST or SGST for a Standalone invoice in Payables when there is no corresponding PO? Shouldn't the system capture the 'State' where the service/goods are delivered?

We are an insurance company and we do not have any of the purchasing modules implemented. Please enlighten.

Thanks,

Shankar