South Korea’s top cryptocurrency exchange, Bithumb, has come under scrutiny after revelations that it raked in more than 140 billion won ($97 million) in undisclosed trading fees, despite advertising the lowest fee rates in the country.
According to data submitted to Rep. Kim Jae-sub of the ruling People Power Party by the Financial Supervisory Service (FSS), Bithumb collected an additional 140.91 billion won in trading fees between February 2023 and February 2024. This figure accounts for a significant portion of the 672.7 billion won in total fees generated during that 12-month period.
“The entire process of signing in and trading failed to inform users about the use of coupons,” Kim said, pointing to what he described as a “clear example of a dark pattern, also known as a deceptive design pattern.”
The issue stems from Bithumb’s failure to properly disclose that customers must register and redeem coupons to access the advertised lowest trading fee of 0.04 percent. In practice, however, most users were charged an average fee of 0.051 percent—a 0.011 percentage point discrepancy from the promoted rate.
Worse, the burden fell disproportionately on older users. Investors in their 60s and above paid the highest average fee of 0.078 percent. Those in their 50s were not far behind, facing charges of 0.076 percent. In contrast, users aged 20 and younger paid just 0.044 percent on average.
Kim said these findings highlight an urgent need for transparency and fairness in how digital asset platforms communicate with customers, particularly older, less tech-savvy individuals who may not be familiar with coupon-based fee reductions.
“The older generations were affected most. Bithumb must provide a clearer and more user-friendly guidebook on coupon usage,” Kim said, adding that the interface had been deliberately designed to obscure cost-saving options from users.
Dark patterns—interface designs intended to trick users into taking actions they might not otherwise choose—are increasingly under fire from regulators worldwide. These include tactics such as automatically adding insurance, hiding opt-out buttons, or, as in this case, obscuring methods to reduce fees.
Kim called on both the Financial Services Commission and the Fair Trade Commission to develop stricter regulatory measures to prevent similar incidents in the future.
“Financial Services Commission and the Fair Trade Commission must also outline measures to prevent similar cases of this sort,” he urged.
The case has sparked renewed calls for greater accountability and regulatory oversight in Korea’s rapidly evolving crypto sector.
