The collective agreement is an essential component of Austrian labor law. This fact is emphasized by the legal institution of after-effect in the sense of the 13th Labor Constitution Act (ArbVG), which extends the legal effects of the collective agreement for a limited time after its expiration to the employment relationships covered before that, subject to dispositivity. Engaging with this fundamental norm of collective agreement law from the 13th ArbVG raises several legal questions. This particularly concerns the area of collective agreement capability and subjection to collective agreements. The after-effect of collective agreements has once again come into focus in legal discussions due to the termination of collective agreements during the restructuring of AUA and Tyrolean Airlines. The work is currently in progress.