This Is It was actually written in 1983?  

Wikipedia says: "Paul Anka, who co-wrote the song, stated that it was recorded in 1983 for a duet intended between he and Jackson on his album Walk a Fine Line under the original title of "I Never Heard".": http://en.wikipedia.org/w... .

He also co-wrote (with Jackson) "Love Never Felt So Good" and wrote the English lyrics to the song "My Way", made famous by Sinatra.

Michael Jackson and Paul Anka wrote it together. When the song was released after his death Paul called the Jackson family telling them about the error. They handed him a check for his part of his interest in making the song. Of course he had to prove he was involved and had a copy of it in his possession.