'I finalised' is correct and usable in written English.
You can use it to demonstrate that you have completed a task. For example, "I finalised the report and sent it to my manager."
"Right now I am finalising things with the university and I cannot comment, he said.
"As I said, the program is not entirely finalised but I hope I do, because he is a very distinguished Australian and the last time I was in New York certainly I did meet with him," Abbott said.
"I'm thinking about the speech day and night but I haven't finalised it yet," he said, correctly declining to reveal anything he might say.
He added that "until such time as the review is finalised I am legally advised that it would be inappropriate for me to comment further".
Rooney told his website: "I'm happy everything is now finalised and I can carry on concentrating on my football".
"I'd say we're not far away from having the details finalised and I'd like to think he'll be in the first team squad".
"I am still finalising the dates and I am not sure of the club team yet as we are still sorting that out.
"The administrative details have not been finalised but I expect the plebiscite to be very similar to the mechanism used for a referendum".
"Everything has been finalised and I have signed a three-year contract," Dikgacoi told the BBC.
