Retain part of the deposit - tenancy dispute service

Tenancy Deposits

Hi , i have sent a request to my tenants to contribute to expenses i had to encounter in making the property good again to let out due to their lack of care. I have asked to contribute to half but they of course refused. I have the Check - in / Interim and Check out inventory plus additional pictures and final invoice i pay to make good again. What is the process should i need to take my request to the dispute service and let them decide how much i should retain from their deposit as they seem not wanting to meet me in the middle.
thanks - Ele