Xiaoming bought a new house in Pu 'er. When did Xiaogang get the ownership of the new house?

I want to ask Xiaoming what can prove Xiaogang's ownership of the new house when he buys it in Pu 'er. According to the relevant information, handling the transfer registration can prove that Xiaogang has obtained the ownership of the new house. Xiaoming bought a new house in Pu 'er, and Xiaogang obtained the ownership of the new house after the transfer registration. As long as he didn't go to Pu 'er Real Estate Registration Center for transfer registration, Xiao Ming didn't get the ownership of the house.