What a CUIT is, and how to confirm a tax registration in Argentina

Ask an Argentine supplier for its tax number and you will get 11 digits, usually written in a two, eight and one pattern with hyphens between the groups. That is the CUIT, and it is the thread that runs through almost every public record about a business in Argentina. This page explains what the number is, how its digits are built, how to spot one that was copied wrong, and how to confirm a company's registration with the tax agency. It also explains why a person's number deserves more care than a company's.

CUIT, CUIL and CDI

Three acronyms come up, and they are related but not the same.

• CUIT, the Clave Única de Identificación Tributaria (single tax identification key). It is assigned by ARCA, the tax agency, to companies and other entities and to people with taxable activity of their own, such as the self-employed and employers.
• CUIL, the Código Único de Identificación Laboral (single labor identification code). It is assigned by ANSES, the Administración Nacional de la Seguridad Social (National Social Security Administration), and identifies workers for social security purposes. A person who has both a CUIL and a CUIT has the same number for each; what changes is which agency uses it and for what.
• CDI, the Clave de Identificación (identification key). ARCA assigns it to people who have neither a CUIT nor a CUIL but need to be identified for certain operations, such as opening a bank account, operating in the financial system or buying registrable property like real estate. According to the government's page on the CDI, it cannot be used to meet tax or social security obligations.

A word on the agency's name. ARCA is the Agencia de Recaudación y Control Aduanero (Tax Collection and Customs Control Agency). Decree 953/2024, published on October 25, 2024, dissolved AFIP (Administración Federal de Ingresos Públicos) and created ARCA as its legal successor. Many of the online services still run on afip.gob.ar addresses, and older documents and invoices mention AFIP. It is the same system.

How the 11 digits are built

A CUIT has three parts.

1. A two-digit prefix that says what kind of holder it is. The prefixes 20, 23, 24 and 27 are used for people. The prefixes 30, 33 and 34 are used for companies and other entities.
2. Eight middle digits. For a person, these are the number of their DNI (Documento Nacional de Identidad, the national identity document), padded with a leading zero when needed. For a company, they are a number assigned by the agency that has nothing to do with any person.
3. One check digit at the end, calculated from the first ten.

Here is an example, written the usual way: 30-12345678-1. This number is invented for this page. The prefix is a company prefix, and the middle digits are simply one to eight in order, picked because nobody would mistake them for a real registration.

How the check digit works

The last digit exists to catch copying mistakes. It is calculated with what mathematicians call a modulus 11 check, and the steps are easier to follow in words than in a formula.

Take the first ten digits, the prefix and the middle eight. Multiply each one by a fixed weight, working from left to right. The weights are 5, 4, 3, 2, 7, 6, 5, 4, 3 and 2. Add up the ten results. Divide that total by 11 and keep only the remainder. Subtract the remainder from 11, and what is left is the check digit.

Two cases need a rule of their own. If the subtraction gives 11, the check digit is 0. If it gives 10, which does not fit in a single digit, that combination is not issued; the agency gives the holder one of the alternative prefixes instead (such as 23 for a person or 33 for a company), which changes the sum and produces a usable digit. That is one reason the alternative prefixes exist.

Run the invented example through it. The first ten digits are 3, 0, 1, 2, 3, 4, 5, 6, 7 and 8. Multiplied by their weights they give 15, 0, 3, 4, 21, 24, 25, 24, 21 and 16, which add up to 153. Eleven goes into 153 thirteen times with 10 left over. Eleven minus 10 is 1, so the check digit is 1, and the full invented number reads 30-12345678-1.

What the check digit can and cannot tell you

A failed check is useful: it tells you a digit was mistyped or two digits were swapped somewhere between the invoice and your spreadsheet. A passed check proves much less. It shows only that the 11 digits are arithmetically consistent. It does not show that the agency ever issued the number, that it is active, or that it belongs to the company in front of you. Anyone can produce a number that passes. To know who a CUIT belongs to, you have to ask the agency.

How to confirm a company's registration with ARCA

ARCA's public registration certificate, the constancia de inscripción, is free and takes a few minutes.

1. Get the CUIT from a document the company gave you, such as an invoice, a quote or a contract. Copy all 11 digits.
2. Open ARCA's constancia page and enter the digits without hyphens, then type the security code shown on screen. This public query does not need a clave fiscal (the agency's login).
3. Read the certificate. It shows the razón social (registered legal name), the taxes and regimes the CUIT is registered for with their dates, such as IVA (value added tax), Ganancias (income tax) or the Monotributo (the simplified regime for small taxpayers) with its category, the declared economic activities and the domicilio fiscal (the address registered with the agency).
4. Compare it with what you were given. The legal name should match the invoice and the contract. The activities should fit what you are buying. The tax status should fit the invoice type: a business registered for IVA issues type A or B invoices, a monotributista issues type C.
5. Save a copy. Print the certificate to PDF and note the date. It reflects the registration on the day you asked.

If you have an electronic invoice, you can also check that the agency authorized it. ARCA's constatación de comprobantes (receipt verification) asks for the issuer's CUIT, the CAE (Código de Autorización Electrónico, the authorization code printed on the invoice), the date, the type, the point of sale and number, and the total.

When the certificate does not match

A different legal name usually means one of two things: you were given the wrong number, or the company invoices through another entity. Both deserve a direct question before you pay. A query that returns no data, or a certificate with no active tax registrations, also calls for an explanation. For a wider look at a company, including the company registries, the Boletín Oficial and the central bank's debtor register, see our guide to researching a business in Argentina.

Why a person's CUIT is personal data

For a company, the CUIT is meant to be public. It is printed on every invoice and is the key to the registration certificate above.

For a person it is a different matter. The middle eight digits of a person's CUIT or CUIL are their DNI number, so anyone who has the CUIT has the ID number too. Argentina's personal data law, Law 25.326, defines personal data as information of any kind about identified or identifiable people, and a tax ID clearly fits. The law does allow some basic lists, limited to name, DNI, tax or social security identification, occupation, date of birth and address, to be processed without consent, which is part of why these numbers circulate so widely. That exception is narrow, and it does not make spreading someone's number harmless. Our explainer on Law 25.326 covers what the law does and does not allow; for a specific situation, ask a lawyer or the AAIP (Agencia de Acceso a la Información Pública, the data protection authority).

The practical risk is impersonation. A caller or an email that already knows your name, your CUIT and your ID number sounds official, and that is exactly what makes a scam convincing.

Some plain rules:

• Share your own CUIT or CUIL with the people who need it: your employer, your bank, ARCA and the clients you invoice. If you are self-employed, it appears on your invoices because it has to.
• Do not post it on social media, in public comment threads or in open forms that do not need it.
• Never publish anyone else's number. That includes screenshots of invoices or payslips, lists of employees or tenants, and posts calling someone out over a debt. Black out the number before you share any document.
• Use the ARCA and BCRA tools for companies, not for checking up on individuals.
• If you think your own number is being misused, check your own report in the BCRA's Central de Deudores for loans you do not recognize, and contact ARCA.

Quick reference

Before you pay an Argentine company, confirm three things: the check digit passes, the ARCA constancia shows the same legal name you were given, and the registrations on it fit the business and the invoice. More on the region is in our Latin America section.