fifteenth council direct decemb harmon law member state relat turnov tax defer introduct common system ad tax hellen republ eec council european commun regard treati establish european econom commun articl thereof regard propos commiss regard opinion european parliament regard opinion econom social committe greek govern inform commiss juli technic econom reason unabl introduc common system ad tax januari date set articl conjunct annex xii act access greek govern request introduct ad tax defer year present greek tax system greek govern request compli technic reason adopt direct articl earliest opportun januari latest hellen republ put effect measur compli direct eec eec eec direct adopt adopt relat common system ad tax articl commiss decemb present council european parliament report progress made hellen republ respect work put effect direct refer articl articl direct address hellen republ brussel decemb council presid varfi opinion deliv decemb publish offici journal opinion deliv decemb publish offici journal oj oj oj