Enter the coupon description in the Template Info section, in the text field titled 'Description'.
The content of this field is then displayed on the pass in the following locations:
In iPhone (Apple Wallet):
When you first view the coupon before you tap on Add to put it into Apple Wallet.
2. On the back of the pass after it has been added to wallet.
Note that the space is a little more than in the view above.
If the text is too long, Apple will use ellipsis points to indicate the omission of one or more words. It is therefore recommended to use descriptions of less than 18 characters.
And ALWAYS check what it looks like for both of the screens above before going live.
In Android devices (Google Pay):
The description field is not used anywhere on a Google Pay pass.