De registration of Bulgarian car

@roverbg

Officially, while you had no usage of the vehicle for 10 years, you still own the vehicle (as you probably didn't bother with a transfer at the notary, and you didn't de-register at KAT). Let's hope that it really was used for spares, rather than someone sneakily repairing it and running around on your plates incurring all manner of fines. :-)

While I don't know how this works, I'd suggest you just go to your local KAT with all the relevant documentation (including, ideally, the sale receipt and the license plates) and a translator/helper (50 leva ish). At the very least, you can explain the situation, and they'll tell you the process/requirements for de-registration.

My guess is that they would accept a sworn (notarized) declaration that says more-or-less what your posting says. My local notary is very helpful, I write something vaguely official sounding (testifying to my personal info / company info, ownership of vehicle x, all the deets of the disposal, my reason for paying tax for 10 years after disposal... and confirming that the vehicle is no longer in my possession) and run it through Google Translate... and they put it in proper Bulgarian and make it look Bulgarian official with a fancy stamp on it. Last time I did this it was about 40 leva.

Did you own the car in your own name or via a company?  If the latter, you're talking about an asset of the company, which has to be disposed of in the correct official manner...