How the Tax Code Works

Discover the calculation algorithm of the Italian Tax Code

Tax Code Structure

RSS

MRA

H501

RSS3 letters from surname (consonants + vowels)

MRA3 letters from name (1st, 3rd, 4th consonant if 4+, otherwise first 3)

852 digits of birth year

C1 letter of month (A=Jan, B=Feb, ... T=Dec)

152 digits of day (+40 for women)

H5014 characters of cadastral code

S1 control character (CIN)

Month Codes

JanuaryA

FebruaryB

MarchC

AprilD

MayE

JuneH

JulyL

AugustM

SeptemberP

OctoberR

NovemberS

DecemberT

Day Rule

👨 Males

Birth day from 01 to 31

15 → 15

👩 Females

Birth day + 40 (from 41 to 71)

15 → 55

What is Omocodia?

Omocodia occurs when two people have the same calculated Tax Code. The Revenue Agency resolves this by replacing some digits with letters.

Substitution table:

0→L1→M2→N3→P4→Q5→R6→S7→T8→U9→V

Control Character (CIN)

The last character is calculated with an algorithm that verifies the correctness of all previous characters. It is a letter from A to Z calculated using odd and even value tables.