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Fiscal Code Structure

The Italian Fiscal Code is a 16-character alphanumeric string that uniquely identifies a person for tax purposes. Once you understand how it''s built, you can read gender, date of birth and birthplace directly from the string itself.

1. Layout

R  S  S  M  R  A  8  5   T    1  0  A  5  6  2  S
|  |  |  |  |  |  |  |   |    |  |  |  |  |  |  |
└──┴──┘  └──┴──┘  └──┘   ┴    └──┘  └──┴──┴──┘  ┴
surname    name   year  month  day   belfiore  check
 (3)       (3)    (2)    (1)   (2)     (4)      (1)
Position Length Content Example
1–3 3 chars Surname (consonants, then vowels) RSS
4–6 3 chars Name (consonants, then vowels) MRA
7–8 2 digits Year of birth — last 2 digits 85 → 1985
9 1 char Month of birth (letter code) T → December
10–11 2 digits Day of birth (females: day + 40) 10 → day 10
12–15 4 chars Belfiore cadastral code of birthplace A562
16 1 char Check character S

2. Surname (positions 1-3)

Consonants come first (in order), then vowels. If there aren''t enough characters to fill three positions, X is used as padding.

Surname Consonants Vowels Code
Rossi R, S, S O, I RSS
Re R E REX
Fo F O FOX

3. Name (positions 4-6)

Names with 4 or more consonants follow a special rule: take the 1st, 3rd, and 4th consonant. For all other names, the same consonants → vowels → X padding rule applies.

Name Consonants Code
Mario M, R MRA (M + R + vowel A)
Luca L, C LCU (L + C + vowel U)
Alessandro L, S, S, N, D, R LSN (1st, 3rd, 4th consonant)

4. Month (position 9)

Each month is mapped to a fixed letter to keep the field purely alphabetic.

Letter Month
A January
B February
C March
D April
E May
H June
L July
M August
P September
R October
S November
T December

5. Day (positions 10-11)

  • Male: the actual day of birth, zero-padded (01–31)
  • Female: day of birth plus 40 (41–71)

This trick lets you determine gender unambiguously just from two digits.

6. Belfiore code (positions 12-15)

A 4-character code that identifies the birthplace:

  • Italian municipality: one letter + 3 digits, e.g. A562 (Rome) or H501 (also Rome, different district)
  • Foreign country: always starts with Z + 3 digits, e.g. Z614 (Venezuela)

The full dataset — ~7 800 Italian municipalities plus ~260 foreign countries (including historical ones like the USSR and Yugoslavia) — is embedded in the library. No external lookup needed.

7. Check character (position 16)

The final character is a checksum computed from the first 15 characters:

  1. Characters at odd positions (1, 3, 5, …) are mapped through a non-linear lookup table
  2. Characters at even positions (2, 4, 6, …) use their ordinal value (0–25 for letters, 0–9 for digits)
  3. Sum all values, take modulo 26, and convert to a letter (A = 0, B = 1, …)

FiscalCodeValidator.IsValid always verifies this character automatically — you don''t need to compute it yourself.

8. Omocodia

When two people would share the exact same CF — same name, same birthdate, same birthplace — one or more of the numeric digits in positions 7–8 and 10–11 are replaced with a letter using a fixed substitution table:

Digit Letter
0 L
1 M
2 N
3 P
4 Q
5 R
6 S
7 T
8 U
9 V

Note

Omocodia variants are not yet supported by this library. Standard Codici Fiscali (with digits in all numeric positions) are fully handled.