How to get a certificate of official tax residency in Bulgaria ?

@Saxio

Excellent question. I am still struggling to get one. Your landlord has to go with you to the Migration department or has to have a notarized declaration that he/she will authorize you to live at her property. Without this document, you won't be able to get an NLCH number  and anything else for that matter. If you don't speak Bulgarian, bring someone who does at the Migration department. Then of course you need a private health insurance to show the government that you won't depend on their public health care and a proof of funds. So far, that's what I have understood. Not easy.