My letter just says it as KIT ID. seems like its composed of the year month and some number.
not sure what it means though.
I was wondering this same thing, so I did a bunch of Google searches about it a few days ago. Breakdown:
Client ID number: Number assigned to someone for their dealings with CIC while inside Canada. Not used by Canadian visa offices abroad.
File Number: Number assigned to your application/file by your overseas visa office once they have received your file. Not used by any CIC offices within Canada.
Kit ID number: Since inland and outland Canadian visa offices use different ways to identify applicants' files (client ID versus file number, for example), the Kit ID number is what the inland offices use to refer to applications in any correspondence between them and the outland offices. It's a universal way of identifying an application package. It's not often even mentioned though, since obviously we as applicants/sponsors always just use client IDs when contacting inland CIC, and file numbers (once we get them) when dealing with outland Canadian visa offices.
Example answer I found via Google: "Usually the KIT ID # is for application done outside Canada. Is it for immigration purposes of when they transfer the files over to the country of the person being sponsored. In visa offices in the other countries they have a different system than CIC here and with that KIT ID # is how to correspond." Thread (see last reply): immigration.ca/discussion2/topic.asp?TOPIC_ID=26314. That link keeps breaking every time I edit this post, but just toss http:// infront of it.
So, in theory, you could technically use your Kit ID number when corresponding with your outland office, if you don't have your actual file number yet (i.e. haven't received AOR yet). In theory. Obviously I've never done this, myself.
EDIT: @ QCSunshine: 1) Your receipt number is very different from your file number. You won't get your file number until you receive your AOR from your visa office. 2) I don't have a clue about French, but it makes sense that "ID de la trousse" would have translated into "application number", since your Kit ID number is just a number assigned to your application package to identify it.
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