With the Variable Symbol function, you can assign a VS to the transaction when paying at the terminal. For example, if you issue invoices to your customers, they can pay them at your terminal by card and you can use the VS to specify which invoice the payment relates to.
This is an extension of the function Sale. After selecting the Sales function, you just need to enter the Variable Symbol, then the amount and complete the payment as with a standard sale. The Variable Symbol will print below the amount on the receipt.
Sales - Variable symbol