If you need a new payment type- you will be able to change a button that you might not be using on your 4POS scan.
Lets say that you don't accept CHEQUES and you would like a payment type for VOUCHERS.
In your Back Office under --> Store setup and security --> More Maintenance --> Maintain Language / Translation
From there you are able to change existing buttons / Back office headings ect. - I would create a new language and change in POS the CHEQUE SALE to VOUCHER
Next step in to go to --> Store setup and security --> General Parameters --> no.4 = Language translation, needs to be set on the language you have created