You can display the last four digits of a credit card 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 both on the Show Payment Method and Show Credit Card Number under the Order Details.
Step 4: Click on the Save button.