• Personal identification number (PIN) is obtained by all newborns, including those abroad, after their registration in the population register of the municipality at the permanent address of their parents.
• The municipality issues birth certificates of children with PIN entered on the basis of birth certificate from local authority civil status - translated into Bulgarian and certified in Ministry of Foreign Affairs (for those born abroad).
• Foreign documents must be submitted to the office of the civil status of the Bulgarian community in person, by proxy or by the Bulgarian diplomatic and consular missions of the Republic of Bulgaria abroad.
• PIN acquire and all persons who have restored Bulgarian citizenship and who have made the choice of a permanent address in Bulgaria.
• Persons who possessed PIN before their release from Bulgarian citizenship restore and their PIN, along with the restoration of their citizenship.

• Birth certificate
• application for elective permanent address in Bulgaria(for people who acquired Bulgarian citizenship by descent or naturalization)
• certified copy of the certificate for obtained Bulgarian citizenship((for people who acquired Bulgarian citizenship by descent or naturalization)

A list of municipalities in Bulgaria where the personal identification number is issued:
http://infobulgaria.info/directory.php?cat=92

Every Bulgarian citizen has a personal identification number (PIN) - a unique number that has come to be used as an identifier for individuals within Bulgaria.

There is no fee for issuing Bulgarian personal identification number.

The personal identification number is valid forever.

Please attach documents which can be used by people who would like to follow this procedure.    

Please attach sample completed documents which would help other people who would like to follow this procedure.    

Within 7 days from the date of birth of a child is issued personal identification number.

Videos explaining the procedure or to fill the applications. 
Attach videos using the following tag <&video type="website">video ID|width|height<&/video&> from external websites.
Please remove the "&" inside the tags during implementation.
Website = allocine, blip, dailymotion, facebook, gametrailers, googlevideo, html5, metacafe, myspace, revver, 
sevenload, viddler, vimeo, youku, youtube
width = 560, height = 340, Video ID = Can be obtained from the URL of webpage where the video is displayed.
e.g In the following url "http://www.youtube.com/watch?v=Y0US7oR_t3M" Video ID is "Y0US7oR_t3M". 
	

The first six digits correspond to the date of birth (YYMMDD).Since the year of birth are separated only two numbers can be coded only the years between 1900 and 1999. Other years are presented in the following way:

• for those born before 1 January 1900 to the month is added the number 20
• For born after 31 December 1999 to 31 December 2099 to the month is added to the number 40.
  

The next three digits (seventh, eighth and ninth) have information about the area in Bulgaria, and the birth order as the ninth is even for a boy and odd for a girl. Seventh and eighth are randomly generated according to the city, and repeats of 00 and 88 are impossible.

• Date of birth
• Place of birth

Bulgarian personal identification number (abbreviated as PIN or ??? in Bulgarian) is a 10-digit number that is unique for each Bulgarian citizen or resident alien.PIN is obtained at birth in hospital or subsequently - when issuing birth certificates. PINs were introduced in 1977 and are used in virtually all dealings with public service agencies, and often with private businesses.

Personal identification number must receive and persons who acquired Bulgarian citizenship by descent or naturalization, after being registered in the municipality in their permanent address in Bulgaria.
In the municipalities they provide a certified copy of the certificate for obtained Bulgarian citizenship issued by the Directorate "Bulgarian Citizenship" of the Ministry of Justice, together with the application for elective permanent address in Bulgaria.

PINs are also printed on Bulgarian identity cards and passports, under the heading "???/Personal number".

http://en.wikipedia.org/wiki/National_identification_number
http://www.mfa.bg/en/pages/56/index.html
http://www.demographic-research.org/volumes/vol6/12/6-12.pdf

More information which might help people.