Kakao is not just the name of the mobile messenger that almost all South Koreans use. It is a Korean substitute for the US’ Uber or Southeast Asia’s Grab. KakaoT, operated by the messenger app company, is by far the most widely used app to hail a taxi, although there are smaller competitors.
Taxi drivers in South Korea won't expect you to tip them, even when they help you with your luggage. As tipping taxi drivers in South Korea is not customary, trying to pay more than your agreed fare may cause confusion and embarrassment.
Deluxe taxis are black in color and have ?? written on the vehicle, usually on the top. They are not available in every city, so don't expect every black taxi to be deluxe. The image below is from Daejeon, where there are no deluxe taxis. Deluxe taxis are in Seoul and Daegu but perhaps other cities as well.
Seoul Taxi TipsAll taxis in Seoul accept credit, debit and cash payments, as well as Tmoney cards. Food, drink and smoking are prohibited during your taxi transfer.
With Kakao T Trip, simply enter the destination and a nearby driver will be notified of the request. The driver will then pick the passenger up and take them to the desired location. Best of all, no foreign language skills are needed to use Kakao T Trip which is especially useful for traveling Koreans.