Most of the five-star hotels in Seoul are omitting mandatory additional fees from the room charges displayed on their homepages, the Seoul city government said Friday.

Seoul Metropolitan Government conducted a survey of 27 hotels rated five stars by the Tourism Promotion Act and found that only three of them show room charges complete with taxes and additional fees to customers. The rest use "drip pricing," a technique where only a part of an item is advertised and the final amount is revealed at the end of the buying process.

In one case cited by the city, a room charge of 697,500 won ($525) was advertised as a special member-only fee at one of the hotels. But the actual price jumped to 843,975 won when taxes and service charges were included.

Seoul officials stressed that drip pricing can lead to consumer confusion when comparing room charges of hotels, as most hotels display the price complete with taxes and service charges.

While it is customary in some other countries to display pretax prices, most products in South Korea display the final price to be paid by the customer.

The South Korean government defines drip pricing as part of "dark pattern" pricing, and in February passed a revision of the Enforcement Degree of the Act on the Consumer Protection in Electronic Commerce, Etc., to ban such techniques meant to deceive consumers. The revision goes into effect in February of next year.

Such dark pattern pricing techniques that will be banned next year also includes raising the membership fees of a service without explicit notification and consent of the user.