"A voucher is a bond of the redeemable transaction type which is worth a certain monetary value and which may be spent only for specific reasons ...
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or on specific goods. Examples include housing, travel, and food vouchers. The term voucher is also a synonym for receipt and is often used to refer to receipts used as evidence of, for example, the declaration that a service has been performed or that an expenditure has been made. Voucher is a tourist guide for using services with a guarantee of payment by the agency.
The term is also commonly used for school vouchers, which are somewhat different." - (en.wikipedia.org 05.10.2019)