This feature gives your customers the option of adding a Tip to the Purchase amount on a Pre-Authorization transaction by indicating the Tip amount on the Merchant copy of the receipt (see receipt example) . It is traditionally used in restaurants and other service-based businesses.
To configure a Tip Line on Pre-Auth receipts ...
To perform Pre-Authorization and Pre-Auth Advice transactions....
If you wish to allow cardholders to add a Tip to Purchase transactions as well as Pre-Authorization transactions, you must enable the Tip Entry feature.