Verify an Italian tax code

What "formally valid" means

This check confirms the code follows the official structure and that thefinal control character is consistent with the other 15 — the same math that catches most typos. It also recognises omocodia variants (codes where some digits are replaced by letters to distinguish two people who would otherwise share the same code).

Keep in mind: a formally valid code is not necessarily a real, assigned one. Only the Agenzia delle Entrate can confirm a code actually belongs to a person — its website offers an official existence check against the tax registry.

Common transcription errors this catches

• The letter O typed instead of the digit 0 (and vice versa).
• A wrong month letter (June is H, not G; the sequence skips ambiguous letters).
• The missing +40 on the day of birth for women (41–71 is normal in female codes).
• Any single-character typo — the control character stops matching.