I have successfully programmed most basic functions on this till but it will not allow us to take a sale with mixed payment type eg a sale for £10.00 where the customer wants to tender a £5.00 voucher and pay the remaining amount in cash. I assume this something to do with the way my charge buttons are programmed but I can't figure out what I'm doing wrong. Can you help ?

in system settings, look for "allow under tender"