Unique citizenship number

The unified civil number (Единен граждански номер, ЕГН) is a 10-digit unique number assigned to each Bulgarian citizen. It serves as a national identification number. An EGN is assigned to Bulgarians at birth, or when a birth certificate is issued. The uniform system for civil registration and administrative service of population (Единна система за гражданска регистрация и административно обслужване на населението; abbreviated: ЕСГРАОН, ESGRAON) regulates the EGN system.

Structure
The initial six digits correspond to the birth date. The first two digits are the last two digits of the year, and the last two digits are the day of the month. For people born between 1900 and 1999 the middle digits are the month number: YYMMDD. For people born before 1900, 20 is added to the month: YY M+20 DD. For people born from 2000, 40 is added to the month: YY M+40 DD.

The next three digits designate the birth order number, the third digit being even for males and odd for females. Each district is assigned a range of three-digit numbers, used consecutively, altering even and odd numbers between males and females born on the particular day. In rare cases a district may not have enough numbers, so numbers are "borrowed" from an adjacent district.

A check digit, calculated from the nine digits using the following algorithm, is appended: 1 Each digit is multiplied by its weight; the weight for the nth digit is 2n modulo 11:
 * {| class="wikitable"

! Position ! Weight
 * 1 || 2 || 3 || 4 || 5 || 6 || 7 || 8 || 9
 * x2 || x4 ||  x8 ||  x5 || x10 ||  x9 ||  x7 ||  x3 ||  x6
 * }

2 The products obtained are added 3 The resulting sum modulo 11 is the check digit. If the result is 10, the check digit becomes 0

Calculation
The first female registered born on 2 January 1975 has number 75 (1975) 01 (January + 0) 02 (2nd) 001 (district has numbers, say, 0-50, and this is first female of this date) & check digit, i.e. 750102001 & check digit. 7x2 + 5x4 + 0x8 + 1x5 + 0x10 + 2x9 + 0x7 + 0x3 + 1x9 = 52; divide by 11, (quotient is 4, ignore), remainder 8 is check digit. So EGN is 7501020018.

Valid EGN numbers

 * 7523169263 — a male, born on 16 March 1875
 * 8032056031 — a female, born on 5 December 1880
 * 8001010008 — a male, born on 1 January 1980
 * 7501020018 — a female, born on 2 January 1975


 * 7552010005 — a male, born on 1 December 2075
 * 7542011030 — a female, born on 1 February 2075

Misuse
In order to easily cross borders criminals have been known to change EGNs. There were 46 such cases detected in March 2005.

Using the EGN system for identification raised some privacy concerns, though they are officially considered personal information and are protected by law.