Gratuity amount for restaurant industry transactions.
This property contains the gratuity (tip) amount of the transaction. This property may be set in the PTechCharge component if you know the amount of the tip before the authorization. Otherwise, you may update the GratuityAmount property of the PTechDetailRecord component after parsing the detail aggregate returned from this component's GetDetailAggregate method. This amount is only sent when the PTechManualSettle component's IndustryType is set to "itRestaurant". If a transaction includes a GratuityAmount, the SettlementAmount must reflect the total of the originally authorized amount, plus the GratuityAmount.
This must be formatted as a dollar amount with a real decimal point, excluding the dollar sign. For instance "12.00"