Word for the money you return to a customer when they give too much

Question

Let's say I'm selling something for $80, someone pay me $100 for it, so I have to give him $20 in exchange.

What is that $20 called?

Answer 1

"Change"

It is a collective noun, so you would refer to the entire $20 as the customer's "change". In example:

$20 is your change.

Is how you would address the customer while handing them the money.