Got a new question for LEN domain auctioneers

If I have a buyer for a domain I am selling that is with an older / Not as well known Registrar
Do I need to give the EPP key to the buyer once it is requested? I want to avoid any mistakes here, I know so far that the buyer needs the key to initiate the transfer, In this case I am assuming after they purchase
the transfer from their registrar also.
Don't know that I have a simple push available to me with my current Registrar as the owner.