How is the NIR control key calculated?

The key equals 97 minus (the 13-digit base number modulo 97). For Corsica, the department codes 2A and 2B are substituted before the modulo, so the base is converted to a number and offset per the INSEE rule. This tool implements that algorithm exactly, including the Corsica case.

Does a valid key mean the NIR is real?

No. A valid key means the number is internally consistent and free of common typos. It cannot confirm the NIR is issued or belongs to a specific person — only the social-security administration holds that record.

What does the first digit of a NIR mean?

The first digit encodes sex: 1 for male and 2 for female (other values exist for special and historical cases). The next two digits are the year of birth, then two for the month, and the rest covers place of birth and an order number.

How is Corsica handled in the calculation?

Corsica uses the alphanumeric department codes 2A and 2B. Before the modulo, INSEE substitutes specific numeric offsets for these (the A and B become defined digit values), so the validator converts them per the official rule before computing the key.

Is my NIR sent anywhere?

No. Validation is entirely client-side — the number never leaves your browser and there are no network requests at all.

France NIR / Numéro de Sécurité Sociale Validator

France NIR validator

The NIR (numéro d’inscription au répertoire), commonly called the numéro de sécurité sociale, is France’s national identification number assigned by INSEE. This tool checks that a NIR is well-formed by verifying its two-digit control key, and decodes its structure — sex, birth month and year, department, commune and order number — so you can read and validate one at a glance.

How it works

A full NIR is 15 characters: a 13-digit base plus a 2-digit control key. The base breaks down as sex (1 digit), year of birth (2), month (2), department of birth (2), commune (3), order number (3). The validator parses each of these fields, then recomputes the key:

key = 97 − (base mod 97)

For births in Corsica the department codes 2A and 2B are alphanumeric, so INSEE defines numeric substitutions that are applied before taking the modulo — the tool handles this special case exactly. If the recomputed key does not match the supplied one, it flags a likely typo.

Example

For a NIR beginning 1 85 12 75…: the leading 1 means male, 85 is the birth year 1985, 12 is December, and 75 is the Paris department. The control key is found by reading the 13-digit base, taking it modulo 97, and subtracting from 97 — the result must equal the final two digits.

Position	Field	Meaning
1	Sex	1 = male, 2 = female
2–3	Year of birth	e.g. 85 → 1985
4–5	Month of birth	01–12
6–7	Department	e.g. 75 = Paris
8–10	Commune	INSEE commune code
11–13	Order number	birth sequence
14–15	Control key	97 − (base mod 97)

A valid key confirms internal consistency only — not that the NIR was issued. Your NIR is processed entirely in your browser; nothing is uploaded, and no government database is queried.