IN_CLOSE
probably means the write is complete. This isn't for sure since some applications are bad actors and open and close files constantly while working with them, but if you know the app you're dealing with (file transfer, etc.) and understand its' behaviour, you're probably fine. (Note, this doesn't mean the transfer completed successfully, obviously, it just means that the process that opened the file handle closed it).
IN_CLOSE
catches both IN_CLOSE_WRITE
and IN_CLOSE_NOWRITE
, so make your own decisions about whether you want to just catch one of those. (You probably want them both - WRITE/NOWRITE
have to do with file permissions and not whether any writes were actually made).
There is more documentation (although annoyingly, not this piece of information) in Documentation/filesystems/inotify.txt.