You can display the tracking numbers on your invoices by following the simple steps below.
Step 1: Open Simple Invoice from your Shopify store’s “Apps” section.
Step 2: Click on the “Templates” on the Simple Invoice dashboard.
Step 3: Click on the Options section, and click on the Show Tracking Number under the Order Details.
If you also wish to show Tracking Company in the same line, you need to create a support ticket with an example order number from the Support section or by clicking here.
Step 4: Click on the Save button.