Company GSTIN is not appearing in the sales invoice. Please help us to update the same.

Hello,

Welcome to QuickBooks Community.

In order to add GST to the invoice, you'll first need to set it up in the Sales Tax Center listed under Taxes from the left menu. The following article includes steps on how to add and edit tax rates: https://community.intuit.com/articles/1145271 .

Once set up, you'll have the option to select the tax if it applies to that particular transaction. 

I hope this helps.