Why dont you ask HP for a copy of the invoice? That's what I did, they were quick and all has gone through ok.
Well I bought mine from HP on-line store, so no till receipt I scanned and sent them the page titled "invoice" that was the last of 4 sections of the ordering process on their own website.
This was rejected so I sent them the Pay-Pal payment confirmations this has been rejected.
Just sent them their email to me confirming acceptance of the order and a copy of the Master Packing Note, but surely they have enough information to be able to check their systems to finds that I bought it from them and they got paid for it?
I ordered from the HP UK Web store.
-- Sent from my HP TouchPad using Communities