There is no need to make any configuration on the Simple Invoice side.

Once you set up your taxes correctly in your Shopify store, Simple Invoice will use these tax settings and automatically display all the required tax details on your invoices.

You can find more information about setting up taxes on the Shopify side by clicking here.

If you make any changes in tax settings in your Shopify admin, only your newly created orders and invoices will reflect this change. Your existing invoices will remain unchanged.