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Direct answers
- What is omocodia (homocode) in the Italian Codice Fiscale?
- Omocodia occurs when two or more different people generate the same fiscal code using the standard algorithm (same surname/name initials, same birth date/place and sex). There are approximately 5,000 new homocode cases per year in Italy. The Revenue Agency resolves each collision by assigning a homocode variant.
- How does the Revenue Agency resolve omocodia?
- The Agency progressively replaces digits in the CF with equivalent letters, starting from the rightmost numeric position toward the beginning. The numeric positions are (right to left): 15, 14, 13, 11, 10, 8, 7. The substitution table is: 0→L, 1→M, 2→N, 3→P, 4→Q, 5→R, 6→S, 7→T, 8→U, 9→V.
- How many homocode variants exist for a Codice Fiscale?
- There are 7 progressive substitution levels (one for each numeric position in the CF), so a maximum of 7 homocode variants. The calculator generates all of them from the base CF. In theory 128 combinations are possible, but the Agency always proceeds in progressive order.
- Does the check digit change with omocodia?
- Yes. Each homocode variant has a different check digit, recalculated on the modified first 15 characters. The calculator regenerates the check digit for each of the 7 variants.
- How can I tell if my Codice Fiscale has omocodia?
- A homocode CF contains letters where digits normally appear (positions 7-8, 10-11, 13-15). For example, if position 15 has 'M' instead of '1', it's a level-1 homocode. The Verify tab of the calculator automatically detects and reports homocode CFs.
Quick answers
Frequently Asked Questions
What is omocodia (homocode) in the Italian Codice Fiscale?
Omocodia occurs when two or more different people generate the same fiscal code using the standard algorithm (same surname/name initials, same birth date/place and sex). There are approximately 5,000 new homocode cases per year in Italy. The Revenue Agency resolves each collision by assigning a homocode variant.
How does the Revenue Agency resolve omocodia?
The Agency progressively replaces digits in the CF with equivalent letters, starting from the rightmost numeric position toward the beginning. The numeric positions are (right to left): 15, 14, 13, 11, 10, 8, 7. The substitution table is: 0→L, 1→M, 2→N, 3→P, 4→Q, 5→R, 6→S, 7→T, 8→U, 9→V.
How many homocode variants exist for a Codice Fiscale?
There are 7 progressive substitution levels (one for each numeric position in the CF), so a maximum of 7 homocode variants. The calculator generates all of them from the base CF. In theory 128 combinations are possible, but the Agency always proceeds in progressive order.
Does the check digit change with omocodia?
Yes. Each homocode variant has a different check digit, recalculated on the modified first 15 characters. The calculator regenerates the check digit for each of the 7 variants.
How can I tell if my Codice Fiscale has omocodia?
A homocode CF contains letters where digits normally appear (positions 7-8, 10-11, 13-15). For example, if position 15 has 'M' instead of '1', it's a level-1 homocode. The Verify tab of the calculator automatically detects and reports homocode CFs.