It is just a paper that the manufacturer should give along the other papers that belong to the car when it was sold. For me it was necessary, without it registration would have been impossible.
I used a special car importer, who did the paperwork/sales and arranged transport for the car. Then I picked up the car myself, I did the initial declaration of import online at the importer’s house and then I drove to the inspection center (without plates, I should not have done that…) and started the registration process. I got temporary plates immediately and drove home.
Soon after that I received email where they asked to scan and send the receipts for the payments so they could calculate proper import tax amount. At this point I could have provided other documentation too, such as the Declaration of Conformity paper but I had already provided it at the inspection center since it came with the car.
After that it took about three months to get the car tax amount, just because this particular car was a rare one (only 4 or 5 imported to here before it). 2005 A4 1.8t Quattro manual trans. and non-leather sports interior. It had pretty much everything like I wanted except color. I would have preferred black… but there was not one for sale then. It is not my main vehicle but something that I’ll try to keep forever…