From memory, it may be different these days.
I had to go to a Notary to sign my car over to my Company.(Strange as it may seem).
I also remember going to an Insurance Office to get a Certified Valuation on the car, as there was a payment made to Kat based on the value of the car.
The 2 things above are not done at the KAT Office.
Check your car documents yourself to verify the chassis and engine numbers tally.
They do check that you have, triangle, fire extinguisher and first aid kit.
That was about 6 years ago, so regulations may now have changed. I took a Bulgarian speaker with me, but it took a day. Also, check the documents, which you receive, as any discrepancies, may show up the following year, when you go for your Annual check.