Isikukood

Isikukood is the Estonian personal identification code, an 11-digit national identifier assigned to citizens and residents. It serves as a unique, lifelong identifier used in public administration, health care, taxation, banking and other services, and is maintained by the Estonian Population Register.

The code format is GYYMMDDSSSC. G is a single digit indicating sex and century of birth; common mappings are 1 (male, 1800–1899), 2 (female, 1800–1899), 3 (male, 1900–1999), 4 (female, 1900–1999), 5 (male, 2000–2099), 6 (female, 2000–2099), with 7 and 8 reserved for persons born in 2100–2199 and 9 reserved for special cases. YYMMDD gives the date of birth. SSS is a serial number distinguishing people born on the same date. C is a control (checksum) digit.

The control digit is calculated from the first ten digits using two weighted-sum rounds and modulus 11: a first weighting set is applied and, if the remainder is 10, a second weighting set is used; if that also yields a remainder of 10, the control digit is 0. This ensures validity and helps detect transcription errors.

Isikukood was standardized after Estonia regained independence and continues to be regulated for accuracy and privacy. Because it embeds birth date and sex, it is treated as personal data and subject to national and EU data-protection rules.