Guide
Common codice fiscale mistakes and how to avoid them
By Codice Fiscale Pro Team · Published on
What are the most common mistakes when calculating a codice fiscale?
The table lists the ten most frequent mistakes with a way to spot each. Examples use the sample code RSSMRA85T10H501O.
| Mistake | How to spot it | How to avoid it |
|---|---|---|
| First name and surname swapped | MRA appears before RSS | The first three letters are the surname, the next three the first name |
| No +40 on the day for a woman | Day 01 to 31 for a woman | For women add 40: day 5 becomes 45 |
| Wrong month letter | Letters such as F, G, I, N, O, Q in position 9 | Use only A, B, C, D, E, H, L, M, P, R, S, T |
| Residence instead of place of birth | Code differs from the municipality of birth | Always use the place of birth |
| Wrong column in the list of municipalities | A code like M1AA instead of H501 | Use "Codice Nazionale", not "Codice Catastale" |
| Same-name municipality in another province | Castro: C337 (BG) or M261 (LE) | Choose the province too |
| Spouse’s surname used | Code differs from the health card | Use the surname at birth |
| Apostrophes and spaces counted as letters | O’Connor that does not give CNN | Ignore apostrophes, spaces and accents |
| O instead of 0, or the reverse | Check letter O against digit 0 in numeric fields | The check character is always a letter |
| Omocodia ignored | Letters in positions that are normally digits | Look at the health card and read what is omocodia |
Why is my calculated code different from the one on my health card?
The most frequent reasons are the spelling of the data and omocodia. Pmi.it (in Italian) lists spaces, apostrophes, double names, special characters and birth abroad among the causes. A code with letters where digits belong is an omocodia variant.
How do you check a code after calculating it?
Check it in three steps, from the quickest to the safest.
- Run it through the code check: it spots wrong structure, date and check letter.
- Read it with the decoder to see that sex, date and place are the ones you expect.
- Compare it with your health card or the Agenzia delle Entrate service (in Italian).
Which mistakes does a formal check catch, and which not?
It catches wrong structure, impossible month or day, and a wrong check letter. It does not catch a wrong but plausible place, a name spelled differently or a code that nobody owns. For those you need an official document. See formal check and official verification.
Sources
- Pmi.it (in Italian): mistakes and variants in the data.
- Agenzia delle Entrate (in Italian): list of municipalities and countries.
Frequently asked questions
What is the most common mistake in hand calculation?
Forgetting to add 40 to the day of birth for women, or swapping first name and surname. Both show up when you reread the two groups of three letters.
Why does my calculated code differ from my health card?
Common causes are a different spelling of the name on documents, a wrong place of birth, the use of a spouse’s surname, or an omocodia code assigned by the Agenzia.
Which letters are never used for the month?
F, G, I, N, O, Q, U, V, W, X, Y and Z never appear. Months only use A, B, C, D, E, H, L, M, P, R, S, T.
How do I check a code after calculating it?
Use the formal check to find structural errors and compare the code with your health card. For an official check use the Agenzia delle Entrate service.
Related guides
- How the Codice Fiscale Is Calculated | Codice Fiscale Pro: The rules for surname, first name, date, place and check letter, with worked examples.
- What Is Omocodia in the Codice Fiscale? | Codice Fiscale Pro: Why two people can share a code and how its digits change into letters.
- Belfiore Code: What It Is and How to Find It | Codice Fiscale Pro: The place-of-birth code for municipalities and countries, with real examples.
- Formal Check vs Official Verification | Codice Fiscale Pro: What an independent site checks and what the Agenzia delle Entrate checks.