The collective agreement is an integral part of the Austrian labor law. This circumstance is underlined by the legal institution of the aftereffect in the sense of § 13 ArbVG as the legal effects of the collective agreement are in a dispensable manner extended for the period after the collective agreement has lapsed for the previously recorded working relationships until a new collective agreement or bargaining agreement comes into effect. The evaluation of § 13 ArbVG as a fundamental legal standard for the collective contract law, raises some legal questions. This applies in particular to the field of collective bargaining ability and the question of being a subject to collective agreements. Since the termination of collective agreements in connection with the restructuring of AUA and Tyrolean Airlines, the aftereffect of collective agreements is again subject to different legal opinions. For the assessment of the case, that a collective agreement has already expired before transfer of business takes place and it is therefore only lasting aftereffect, specially arises the question of the relationship between §§ 13 or 8 Z 2 ArbVG and § 4 AVRAG. There are different opinions among legal scholars. Recent opinions lead to the conclusion, that a transfer of business, that takes place while the collective agreements are already in the phase of aftereffect, cannot cause a collective bargaining change. § 13 does not create a collective agreement affiliation, but it protects the transferred employment conditions generally prior to protection gaps and deteriorations that can be associated with the transfer of business.