Tax Code Structure: The 16 Characters Explained

16 Characters Overview

The Italian Tax Code (Codice Fiscale) consists of 16 alphanumeric characters arranged in a precise sequence that encodes a person's personal data. Each position has a specific meaning and follows well-defined rules established by Presidential Decree No. 605/1973.

This seemingly complex structure is actually an elegant system that allows fundamental personal information to be derived directly from the code, while maintaining a compact and easily memorable format.

Characters 1-3: Surname

The first three letters of the Tax Code derive from the person's surname. The algorithm follows precise rules to extract these letters:

1. Take the consonants of the surname in the order they appear
2. If there are fewer than 3 consonants, add the vowels in order
3. If the surname has fewer than 3 letters total, add the letter X

Characters 4-6: First Name

Characters 4 to 6 derive from the person's first name, but with a special rule that differentiates this calculation from that of the surname:

• If the name has 4 or more consonants: take the 1st, 3rd, and 4th consonant
• If the name has fewer than 4 consonants: apply the same rule as for the surname

Characters 7-8: Birth Year

Characters 7 and 8 represent the last two digits of the birth year. This is the simplest and most direct part of the code.

Character 9: Birth Month

The ninth character is a single letter indicating the month of birth. Each month corresponds to a specific letter according to this table:

Characters 10-11: Day of Birth and Gender

Characters 10 and 11 encode two pieces of information simultaneously: the day of birth and the person's gender.

• Men: the day of birth as is (from 01 to 31)
• Women: the day of birth + 40 (from 41 to 71)

Characters 12-15: Municipality Code

The four characters from position 12 to 15 represent the cadastral codeof the municipality of birth:

• One letter + three numbers for Italian municipalities
• Letter Z + three numbers for foreign countries

Character 16: Control Character (CIN)

The last character of the Tax Code is the CIN (Control Internal Number), an algorithmically calculated letter that serves to verify the code's correctness.

This mechanism helps detect transcription errors such as single incorrect characters or swapped adjacent characters.