The denomination effect is a cognitive bias where individuals are less likely to spend money in large bills compared to an equivalent amount in smaller denominations or coins. Larger bills are often overvalued, acting as a self-control mechanism to deter spending, as people are reluctant to "break" them and lose track. Smaller units are undervalued and spent readily.Priya Raghubir and Joydeep Srivastava's (2009) foundational research demonstrated less spending from a single $5 bill than from five $1 notes. Large denominations are perceived as less fungible, serving as a pre-commitment strategy to save. If this self-control fails, a "what-the-hell" effect can lead to increased spending. Smaller denominations are also harder to monitor and recall, contributing to easier spending.Recent studies introduce important nuances:

• The "denomination-tipping effect" (Zenkić et al., 2023) reveals a reversal in social contexts; embarrassment makes consumers less likely to tip smaller denominations.
• The "denomination–spending matching effect" (Li & Pandelaere, 2021) suggests consumers prefer denominations that match the purchase price (small for small, large for large), driven by "denomination fit" that boosts satisfaction.

Practical applications include retailers using smaller change to encourage purchases and consumers carrying mismatched denominations to curb spending. Investors should evaluate a company's holistic value rather than just share price to avoid this bias.