The Receipt/Invoice templates will automatically show taxes charged on orders. Shopify calculates the tax amounts based on your Shopify tax settings. Our documents automatically display the tax and its corresponding rate.
Check Shopify admin settings
If you don't see taxes in your invoice, double-check your tax settings in the Shopify admin. You can do that on this page: https://shopify.com/admin/settings/taxes
Once taxes are set up in the Shopify admin, they will automatically display during checkout, in emails, and in the invoices.
Important
Shopify will not update old orders when you make tax changes, so only new orders will show the new taxes you have set up.