The U.S.-traded company has received queries from the Hong Kong stock exchange about aspects of its structure, including a user trust set up in 2019, the report said.
Nio, whose shares were down about 2% in premarket trading, did not immediately respond to a Reuters request for comment.
Reuters had reported in March that the company was looking to list in Hong Kong as soon as this year.
Nio said on Tuesday it was planning to sell up to $2 billion worth of its American depository shares.
(Reporting by Eva Mathews in Bengaluru; Editing by Aditya Soni)
