SUM is the member platform launched by the largest used car business alliance in Taiwan, SUM Alliance. This Android app provides exclusive discounts for car buyers and owners for maintenance services. It also offers the members the ability to check their transaction history and maintenance records for their cars.

One of the best features of the app is the exclusive discount coupons that are updated regularly for the members. The transaction history feature allows the users to check their car's registration details, warranty dates, certifications, free towing services, and the dealership they purchased the car from. The maintenance history feature allows the users to check their car's maintenance records, including repair items, repair costs, warranty locations, and mileage when the car was serviced.

Overall, SUM is a useful app for car buyers and owners in Taiwan who want to keep track of their car's transaction and maintenance history while also enjoying exclusive discounts.