cashback
money you get back after a purchase, or cash from a card at a shop /ˈkæʃbæk/
bargain
something that costs less than usual; a good deal /ˈbɑːɡɪn/
invoice
a document asking for payment for goods or services /ˈɪnvɔɪs/
currency
the system of money used in a country /ˈkʊrənsi/
Examples
“Can I get cashback with this card?”
“This coat was a real bargain — only €30!”
“Please send me an invoice for the work.”
“The currency in Japan is the yen.”