Vouchers are certificates or tickets redeemable like cash given to consumers for only definite reasons and they only are for exact items like travel, education, food and housing to name a few. The restrictions on vouchers will be printed on them and they are not vague whatsoever. You will know exactly what services or goods you can obtain from your voucher as well as the dollar value of it. Some restrictions can be in such fine print on the back of the voucher you wonder if you can redeem them at all, but normally redemption is quite simple if you stick with exactly what is stated on the front of the voucher. If the voucher states one gallon of milk, than that is all you are entitled to.
Nowadays with the Internet being one of the most prominent option for consumers to buy and sell goods; e-vouchers actually exist. These vouchers are for shopping online only and normally come in code form. During the checkout phase of the merchandiser you are purchasing from there will be an option to put in voucher codes which will automatically calculate in your total. Good luck shopping and do not forget to use those vouchers.