TAX PROVISIONS - HARMONIZATION OF LEGISLATION - TURNOVER TAXES - COMMON SYSTEM OF VALUE-ADDED TAX - PROVISION OF SERVICES - BASIS OF ASSESSMENT - CONSIDERATION , DIRECTLY LINKED TO THE SERVICE , CAPABLE OF BEING EXPRESSED IN MONEY AND HAVING A SUBJECTIVE VALUE ( COUNCIL DIRECTIVE 67/228 , ARTS 2 AND 8 ( A ): ANNEX A , POINT 13 )