This article presents an analytical and comparative study of criminal damage in Iranian and English law, with a focus on financial thresholds, the phenomenon known as the “cliff-edge effect,” and the role of final civil judgments in criminal proceedings. The cliff-edge effect refers to a situation where a minor quantitative change in legal indicators—such as a slight increase in financial damage—produces a sudden qualitative shift in the type or severity of punishment. In Iran, Article 677 of the Islamic Penal Code (1996, amended 2024) sets a fixed threshold of 330 million rials, where crossing this limit abruptly transforms the sanction from a fine to imprisonment. Such a sudden change challenges the principle of proportionality, undermines legal predictability, and may affect jurisdiction. By contrast, English law under the Criminal Damage Act 1971 follows a gradual model: the amount of damage influences jurisdiction and sentencing ranges without triggering a sudden change in the nature of punishment. The findings indicate that a final civil judgment on damages, particularly in borderline cases, can directly affect both the degree of punishment and the competent court. In the absence of a clear coordination mechanism, this overlap risks inconsistency or conflict between civil and criminal rulings. The study proposes reforms such as introducing graded sentencing under Article 677, automatic adjustment of thresholds in line with inflation, standardized expert valuation of damages, and explicit statutory recognition of civil judgments in criminal proceedings. These reforms would enhance proportionality, coherence of judicial practice, and effective victim protection.