🪪 Spanish DNI / NIE Validator

About the Spanish DNI / NIE Validator

Every Spanish DNI (Documento Nacional de Identidad) ends with a control letter calculated from its 8 digits. This tool calculates that letter instantly and tells you, as you type, whether a DNI, NIF or NIE is valid.

It is useful for anyone who needs to check Spanish identification numbers before entering them in a form, a contract, an invoice or a database — and it shows the calculation step by step so you can verify it yourself.

Key Features

• Letter calculation: type the 8 digits and get the control letter immediately.
• Instant validation: type the full number with its letter and see right away if it is correct — and which letter it should be if not.
• NIE and special NIF support: foreign national numbers (X, Y, Z) and special NIFs (K, L, M) are handled too.
• Bulk mode: paste a list of numbers and validate them all at once, then copy the results.
• Tolerant input: spaces, dots and dashes are ignored, lowercase letters are accepted.

How the Control Letter Is Calculated

• Step 1: take the 8-digit DNI number (for a NIE, replace X with 0, Y with 1, Z with 2).
• Step 2: divide it by 23 and keep the remainder (a number from 0 to 22).
• Step 3: look up the remainder in the table below to get the letter.

Example: 12345678 ÷ 23 leaves a remainder of 14, which corresponds to the letter Z → 12345678Z.

Common Use Cases

• Checking a customer's or employee's DNI before issuing an invoice or a contract
• Recovering a forgotten control letter from the 8 digits of an ID card
• Cleaning a spreadsheet or CRM export containing Spanish ID numbers
• Developers testing form validation for Spanish NIF / NIE fields

Tips & Best Practices

• For Spanish citizens, the DNI number followed by its letter is also their NIF (tax ID).
• The letters I, Ñ, O and U are never used as control letters, to avoid confusion with other characters.
• A correct control letter proves the number is well formed, not that it has actually been issued to someone.
• Company tax IDs (former CIF, e.g. B12345678) use a different algorithm and are not covered by this tool.

Privacy & Security

All calculations run locally in your browser. No ID number is sent to any server, stored or logged — you can even use the tool offline once the page is loaded.