As Uzunpınar & Tüfek International Law Office, we provide comprehensive legal consultancy and litigation services in disputes arising from tenancy law. In particular, in rent determination lawsuits filed pursuant to Article 344/3 of the Turkish Code of Obligations, determining whether the tenancy relationship has exceeded the five-year period and assessing the effect of subsequent rent adjustment agreements on this period are of critical importance. In practice, disputes frequently arise regarding whether additional protocols or subsequently executed agreements between the parties restart the statutory five-year period. In this article, we examine the legal consequences of supplementary agreements increasing the rent amount, the circumstances under which a subsequent agreement may be considered a new lease agreement, the evaluation of comparable market rental values, and the current case law of the Court of Cassation and Regional Courts of Appeal. We also discuss from which date a rent determination action may be filed under Article 344/3 of the Turkish Code of Obligations...