It will be on the invoice, when you get that (and then you will be asked to get the payment together), probably won't be on anything until then.
See earlier post. It usually appears earlier in the page's source (use CTRL-U to display in Chrome) than it appears on the rendered page.
And in my case it's incorrect to say that it only appears on the invoice. I saw my VIN --displayed in my account, not in the page source-- well before the final invoice (and in Belgium it's vital, since Tesla was handling the registration and insurance through a broker and that needs the VIN and registration data about the exact model well before the final invoice is emitted). The first time it was displayed in an attached document was in an amended Motor Vehicle Purchase Agreement, although it was later replaced with a document without the VIN (go figure) once the final invoice was made.
In my case, the VIN was assigned more than a week before the ship that had the car arrived in Zeebrugge, while the final invoice was only emitted once the Delivery Centre had confirmed that they received it in a state that would allow them to deliver it (which is what triggered the finalising of the registration/insurance paperwork).
Of course it's possible there is some regional variation with how closely they keep the VIN to their chest (there seem to be a lot of ad-hoc changes to the document flow to adapt to each country's fiscal peculiarities; some of them don't really work well at first).
As I said, in Belgium they need to be more transparent or they wouldn't get anything delivered smoothly, so that helps.
To be fair, the paperwork is emitted by a mysterious beast in Fremont that even the local delivery people fail to understand (I was told to ignore a credit note for the entire amount of the invoice until I received a new identical invoice. Still haven't got that, so in theory I could call up Tesla in 90 days to ask them when they will transfer the funds for that credit note, and have the car for free once that's been settled).