Formal:
* 下次再見 (xià cì zài jiàn) - Literally "see you next time"
* 再會 (zài huì) - A more formal farewell, similar to "goodbye"
Informal:
* 下次 (xià cì) - Literally "next time"
* 再見 (zài jiàn) - A more casual farewell, similar to "see you later"
Other options:
* 等下次 (děng xià cì) - "Wait until next time"
* 期待下次見面 (qídài xià cì jiàn miàn) - "Looking forward to seeing you next time"
The best choice will depend on your relationship with the person you're speaking to and the situation.