Mormons have no such belief.
You said Mormon have no such beliefs. I think you are incorrect.
I have read that deceased persons can be baptised by proxy in the Mormon Temple. And Mormons are encouraged to do genealogy research for their ancestors and get as many of them baptised by proxy as they can. I am asking if it is more a matter of expense (how much does it cost?) or lack of information on the deceased ancestor? Thus, the genealogy database kept in Salt Lake City.