Apologies! Feel free to resubmit at any time. ^^
how do I prove ownership?
I don't require anything up front, just needed for the group to side with you if someone else contests the transfer (e.g. someone from the original breed claiming they'd already purchased the horse and didn't approve the transfer).
For breeds, screenies of their docs (normally groups have a journals/spreadsheets where IDs and owners are listed), or alternatively or for adoptables just a screenie confirming you were given ownership (e.g. the designer responding that a payment is complete, etc.).