Young will be working alongside Terry Doyle, the partner at the firm who was instrumental in setting up the York office 18 years ago.
Doyle said: "We are delighted to welcome Simon to the firm. He has that wonderful combination of technical ability and expertise together with an appetite for commercial success and a positive outlook.
"This is the right development for us and it has come at the right time. I am looking forward to working with Simon and continuing to develop our practice."
Young added: "While I’m an accountant and deal with figures, I really feel I’m there to look after clients. I like the philosophy of this firm and I am keen to be part of their future success. I am pleased to be on board."