voucher
as defined in Council Directive 2006/112/EC of 28 November 2006 on the common system of value…, Article 30a, point (1)
an instrument where there is an obligation to accept it as consideration or part consideration for a supply of goods or services and where the goods or services to be supplied or the identities of their potential suppliers are either indicated on the instrument itself or in related documentation, including the terms and conditions of use of such instrument