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Mexico – National ID Number (CURP)

The National ID Number (CURP) is an 18-character alphanumeric code. The CURP is an ID number provided by the Mexican government to Mexican citizens and residents. It is similar to the U.S. Social Security number and is required for most government services. The code is structured as follows:

  • Four letters from the individual’s legal name:
    • First letter of the paternal surname
      • If the first letter of the paternal surname begins with Ñ, the letter X is used.
    • First internal vowel of the paternal surname
      • If the paternal surname does not have a first internal vowel, the letter X is used.
    • First letter of the maternal surname
      • If the subject does not have a second surname, the letter X is used.
    • First letter of the given name
  • The individual’s six-digit date of birth in YYMMDD format
  • One letter indicating the individual’s gender: “H” for male (hombre) and “M” for female (mujer)
  • The two-letter abbreviation of the state where the individual was born 
    • If the individual was born outside of Mexico, “NE” (Nacido en el Extranjero) is used here.
  • Three letters from the individual’s legal name:
    • First internal consonant of the paternal surname
      • If the first internal consonant of the paternal surname is Ñ or does not exist, the letter X is used.
    • First internal consonant of the maternal surname
      • If the first internal consonant of the maternal surname is Ñ or does not exist, the letter X is used.
      • If there is no maternal surname, the letter X is used
    • First internal consonant of the given name
      • If the first internal consonant of the given name is Ñ or does not exist, the letter X is used.
  • One character to avoid duplicate CURPs
    • Individuals born before 2000 are assigned a number from zero to nine.
    • Individuals born after 2000 are assigned a letter from A to Z.
  • A one-digit checksum

Figuring Out a CURP from Personal Details

To better understand the CURP, consider an individual with the following details:

  • Name: Juan Carlos Hernandez Garcia
  • Gender: Male
  • Date of birth: May 6, 1982
  • Place of birth: Ensenada, Baja California, Mexico
  • Final two digits of CURP assigned by the Mexican government: 09

Given Hernandez’s personally identifiable information (PII), his CURP will be:

HEGJ820506HBCRRN09

Important Exceptions

The names José and María are typically ignored when constructing ID numbers. Read more about this in the Sayari Learn article on Mexican naming conventions and ID numbers.

Consider an individual with the same PII as Juan Carlos Hernandez Garcia but with the name José Alonso Hernandez Garcia. In this instance, José is ignored when constructing the CURP and Alonso is used as the given name instead. The resulting CURP will be:

HEGA820506HBCRRL09

Rules to Remember

When constructing the CURP, there are several additional rules to keep in mind:

  • If a woman is married, her maiden name is used.
  • If a person’s name includes a letter featuring an umlaut ( ¨ ) that needs to be used in the ID number, the letter will appear in the CURP without the umlaut.
  • If a special character such as a slash ( / ), dash ( – ), or period ( . ) appears in the location of a letter that would be used in the CURP, the letter X is used.
  • If the first four letters of the CURP would form an inappropriate word, the second letter will be replaced with an X. A list of inappropriate words and their substitutions can be found in Anexo 2 on page 62 of the Mexican government’s CURP guide.

Thanks for Reading!