Eight of those have been told they will not be receiving the offer of a new contract following the defeat to Livingston in the play-off semi-final, while a further five will return to their parent clubs after the conclusion of their loan deals.
Among those not staying are first-team regulars Willo Flood, Mark Durnan and Grant Gillespie.
Dutch midfielder Jordie Briels is another heading for the exit door, along with January flop Emil Lyng.
Former Rangers centre-back Bilel Mohsni will leave Tannadice just two months after joining on a short-term deal.
Youngster Cammy Ballantyne has been told he will not receive a new deal after spending time on loan at Montrose.
Celtic right-back Anthony Ralston heads up the list of those heading out following the conclusion of their loan deal.
There’s also Thomas Mikkelsen (Ross County), Harry Lewis (Southampton), Craig Slater (Colchester United) and Brandon Mason (Watford).
It had previously been confirmed that youngsters Logan Martin, Dom Mcmeekin Brett Long and Graham Taylor would all be leaving at the end of the campaign.
United confirmed in a statement that talks are ongoing with other players on expiring deals.
Manager Csaba László said: “I would like to thank each of these players for their efforts in the United shirt. I wish them all the best for the future. We are well along the road in the process to improve the squad for next season and fans should expect updates on this soon.”