The 19-year-old worked under Chiefs coach Steve Komphela for 18 months prior to the latter's move to Amakhosi a year ago.
Maritzburg chairman Farouk Kadodia today confirmed Moon will not be with his club next season.
"The club identified Ryan Moon from the Maritzburg College and we promoted him to our team," said Kadodia at the unveiling of United's new signings at Harry Gwala Stadium.
"Unfortunately we were in negotiations with him and he didn't agree and he will definitely not be with us next season."
Moon's older brother Bryce has just joined the Team of Choice from Mpumalanga Black Aces. The former Bafana Bafana and Mamelodi Sundowns defender is excited that his sibling is heading to the Glamour Boys.
"I'm happy for him, I'm excited he has got the opportunity. I just wish him the best of luck, I am sure he will do well," Bryce tells snl24.com/kickoff.
"I hope he kicks off his career very well, that is the most important thing now. He's worked with those coaches before, they obviously have faith in him if they brought him to Chiefs. So I'm quite positive that they will still nurture him and guide him where he needs to be guided. Yeah definitely I think he has the potential to be a very good striker in the world."
Meanwhile, Maritzburg have extended the contracts of Abia Nale, Deolin Mekoa, Kurt Lentjies, Fortune Makarine and Virgil Vries, while they have released Khumbulani Banda, Menzi Chilli and Mohamed Anas.