Is not a coupon and a voucher the same thing?
Coupon, I should think, is derived from French. And voucher, perhaps, is the English English word for same.
Or what do you say?
Is there a difference or is there none?
In AE, at least, a coupon usually has some type of monetary offer or discount.
"Buy One, Get One Free."
"50 cents off "Ultra White" brand toothpaste.
"20% off your next tire change at Tires R Us. Must be redeemed by October 31."
A voucher, however, is usually a "ticket" distributed in exchange for a product. For example, in the airport, one is given a claims ticket or voucher with an identifying number that corresponds to a badge placed on your bag.
Advertisers may mail out vouchers for new products. If you take the voucher into the store by a certain date, you can pick up a sample of the product for FREE, but there is no purchase involved.
Welfare recipients are allotted food vouchers every month. They can use these to "purchase" foods at representing stores. The types of food they buy with these vouchers must meet state-mandated nutritional requirements.
I'm not sure there is a big difference in everyday UK usage.
Money off voucher, money off coupon both sound the same to me and I think are used interchangeably. Often the word token is used to mean the same thing for example you can buy book or CD tokens which are vouchers you hand over and are taken as payment.
Coupon was the word used when there was rationing during the war and into the 50s.