Tax code verification: when and why to do it

The tax code uniquely identifies Italian citizens in their interactions with public administration. It is assigned by the Italian Revenue Agency (Agenzia delle Entrate) and consists of 16 alphanumeric characters that encode the personal data of an individual (name, surname, gender, date, and place of birth).

Since it is the most commonly used identification code for access to personal data such as income or health information, it is essential to ensure the use of accurate and valid tax codes matching those registered in the Tax Registry.

What is the purpose of verifying the tax code?

The tax code verification confirms that a given code is valid, meaning that it matches the one registered with the Italian Revenue Agency for a specific individual. This correspondence is crucial to prevent administrative errors, fraud, and delays in operations related to contracts and dealings with the Tax Authority.

The verification of a tax code with the Revenue Agency ensures:

• Data accuracy: a key requirement for issuing and transmitting official documents such as electronic invoices and contracts, as well as for maintaining data quality;
• Personal data matching: checking that a tax code actually corresponds to a specific individual helps prevent mistakes and identity mix-ups;
• Tax traceability: the correctness of the tax code is essential for recording all tax-related operations of an individual;
• Fraud and error prevention: confirming the validity (and existence) of a tax code minimizes the risk of interacting with non-existent entities or making administrative mistakes.

Whether it’s for issuing an invoice or filling out a 730 tax return, the accuracy of the tax code is a crucial element in interactions between citizens, businesses, and public administration.

Why calculating the tax code is not enough

The tax code directly corresponds to a person’s personal data:

• The first three letters generally consist of the first three consonants of the surname;
• The next three letters are the first, second, and third consonants of the first name;
• Then two digits corresponding to the last two digits of the year of birth;
• A letter from A to T indicating the month of birth based on a correspondence table;
• Two digits that indicate the day of birth and gender (the date of birth is written as-is for males and with 40 added for females);
• A letter followed by three digits corresponding to the cadastral code that indicates the place of birth (municipality);
• A final letter serving as a control character.

This mechanism may result in identical codes for different individuals, a phenomenon known as homocody. In such cases, the Revenue Agency assigns a new code to each individual to ensure the uniqueness of identifiers.

It is never possible to be certain that a code generated through calculation actually belongs to a specific person. Therefore, online tools that allow you to calculate the tax code using the algorithm described above cannot be considered a reliable source for verifying a tax code.

How to verify a tax code

To verify the actual validity of a tax code, it is necessary to perform cross-checks with the official databases of the Italian Revenue Agency: this is the only way to confirm whether a given code exists and is attributed to a specific person.

For this purpose, the Revenue Agency provides a free online service that allows you to verify the validity of a tax code quickly and easily.

Many organizations that need to check tax codes — from e-commerce platforms to public entities — rarely have the capacity to perform a manual search for each identifier on the Agency’s portal.

When it comes to verifying user data for real-time transactions or updating registries and databases, it is necessary to rely on APIs. For this reason, it is crucial to work with providers specializing in bulk verification and integration services that query the official resources of the Revenue Agency — the only ones that can guarantee the actual validity of the codes being checked.