You can display the tip amount on your invoices by following the simple steps below.
When you activate this option, the Tips are always will be printed as a line item.
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 Order Tip under the Line Items.
Step 4: Click on the Save button.