Keep track of vouchers
Vouchers lists every voucher the company gave a customer and what's left on it; from there you print a voucher or replace a lost one.
This article is still being written: it explains what the screen is for, and its steps are not written yet.
A voucher is a printed code that carries value. The company usually gives one to a customer on a return instead of cash, and whoever holds it can use it at the till. You'll find every voucher under Sales → Vouchers: its number, status, issued value, what's left on it, its expiry date and where it came from.
The page shows for people with the View sales permission, which the owner and the manager have by default. Open any voucher to see where it was used, or press Print voucher. People with Manage vouchers can press Replace voucher when a customer loses theirs: the old code stops working and the remaining value moves to a new voucher.