I have recently purchased a yearling from a well-known stud. He currently isn’t registered with any society or breed groups. I was wondering if he’d be eligible for ACE registration and what paperwork would I need to provide to register him. Does the breeder need to supply the paperwork and send it through or can I do it with a copy of the Service Certificate?

Yes, he is eligible.  A Service Certificate is needed. Follow this link for complete information.

https://acegroupinc.com.au/foal-registration-application/

You will also be required to become a member of ACE Group in order to register your yearling.