To perform a Mexico tax ID number lookup, use the free RFC verifier on the official SAT portal at sat.gob.mx. The SAT (Servicio de Administración Tributaria) is Mexico’s tax authority, and its verifier is the only tool that returns a legally compliant result. For a check that satisfies Mexico’s electronic invoicing rules, you need three things from the counterparty: the RFC itself, the exact registered legal name, and the five-digit fiscal postal code.
How to Run the Lookup on the SAT Portal
Open sat.gob.mx and go to the RFC validation section. The tool offers two modes: a simple RFC-only check and a comprehensive check that validates the RFC together with the legal name and postal code. The comprehensive check is the one that matters, because Mexico’s current CFDI 4.0 invoicing standard requires all three fields to match SAT records for an invoice to be valid.
For the comprehensive lookup, enter:
- The RFC: 12 characters for a business, 13 for an individual.
- The registered legal name (Denominación o Razón Social) exactly as the SAT has it on file. This is character-sensitive, including punctuation and capitalization. One extra space or a missing accent will fail the match.
- The fiscal postal code: the five-digit code tied to the taxpayer’s registered tax address, as shown on their Constancia de Situación Fiscal.
Complete the CAPTCHA and click “Consultar RFC.”
What the Results Mean
If the three inputs align with the SAT’s registry, the system returns a confirmation that the data is valid and consistent with the taxpayer’s proof of tax situation.1EY México. CFDI 4.0: Publication of RFC Verifier That confirmation is what you need before accepting a CFDI from that counterparty.
Two failure messages are worth understanding. “RFC not registered” means the code does not exist in the SAT database at all, which usually points to a typo or to a counterparty that never completed registration. “Data mismatch” means the RFC is real but the legal name or postal code you entered does not match the SAT record. In practice most failures are mismatches, and most mismatches come from stale name or address data on your side. The fix is not to guess: request the counterparty’s Constancia de Situación Fiscal and copy the fields from there.
Getting the Counterparty’s Constancia de Situación Fiscal
The Constancia de Situación Fiscal is the SAT-issued tax status certificate that contains every field you need for the lookup: RFC, CURP (for individuals), full legal name, registered address and postal code, and tax regime.2Portal de Trámites y Servicios del SAT. Constancia de Situación Fiscal Your counterparty generates it directly on the SAT portal or through the SAT Móvil app. The document carries a QR code that links back to the taxpayer’s fiscal identification certificate.
Ask for a current Constancia before you onboard any new Mexican vendor or employee. When the fields come straight out of the SAT’s own document, you are not relying on what someone typed into an email, and your first lookup is far more likely to pass on the first try.
Batch Lookups for Many Vendors
The SAT verifier accepts batch files. Both the RFC-only mode and the comprehensive mode let you upload a plain text (.txt) file in UTF-8 encoding with up to 5,000 entries at once.1EY México. CFDI 4.0: Publication of RFC Verifier For the comprehensive check, each line contains a sequential number, the RFC, the legal name, and the postal code. The tool returns a results file showing which lines passed and which failed, so follow-up is targeted.
Run the batch quarterly if you carry an ongoing Mexican vendor file. Taxpayers change addresses, restructure and rename, and switch tax regimes without notifying every counterparty, and a record that verified cleanly six months ago can quietly go stale.
Also Check the Article 69-B Blacklist
A clean RFC verification confirms the counterparty exists and their data matches. It does not tell you whether the SAT considers that counterparty legitimate. Article 69-B of Mexico’s Federal Tax Code (Código Fiscal de la Federación) authorizes the SAT to presume a transaction never occurred when the invoice issuer lacks the assets, staff, or infrastructure to have delivered the goods or services claimed. When the SAT reaches that conclusion and the taxpayer fails to disprove it, the entity is added to an official definitive list.
Transacting with a listed entity has hard consequences. Invoices from that entity lose their tax effect, every expense you claimed on those invoices becomes non-deductible, and the SAT can reopen audits covering the full history of your dealings with that vendor. The SAT publishes the definitive 69-B list on its portal and in the Diario Oficial de la Federación. Cross-reference any new vendor’s RFC against the list before the first payment, and repeat the check periodically. The standard RFC verifier will not flag 69-B status for you, so build it in as a separate step in your onboarding.
A Quick Read on the RFC Format
You do not need to decode an RFC to verify it, but knowing what a valid one looks like helps you catch obvious errors before you run the lookup.
A business RFC (Persona Moral) is 12 characters: three letters from the company name, six digits for the incorporation date in YYMMDD form, and a three-character Homoclave. An individual RFC (Persona Física) is 13 characters: four letters derived from the person’s name, six digits for the date of birth in YYMMDD form, and a three-character Homoclave.3OECD. Mexico Information on Tax Identification Numbers If a vendor sends you an 11-character string, something is off before you even open the verifier.
There are also generic RFCs used as placeholders. XAXX010101000 covers sales to the Mexican general public when the buyer provides no RFC, and XEXX010101000 covers transactions with foreign residents who have no Mexican tax registration. Two narrower codes apply when a Mexican legal entity has foreign shareholders who are not required to register with the SAT: EXTF900101NI1 for foreign individual shareholders and EXT990101NI1 for foreign legal entity shareholders.4Gob MX. Inscription at the Federal Taxpayer Registry A generic RFC is a placeholder, not a deduction tool: an invoice issued to a generic code cannot support a tax deduction for the buyer. If you need the expense to be deductible in Mexico, your counterparty needs their own individually issued RFC.
What Happens If You Skip the Lookup
The most direct cost is the loss of your deduction. Under CFDI 4.0, if the RFC, legal name, tax regime, or fiscal postal code on an invoice does not match SAT records, the invoice is invalid and the expense cannot be claimed. That inflates taxable income and increases the income tax (ISR) bill. Across a large Mexican vendor base, a pattern of invalid invoices adds up quickly.
The SAT also imposes administrative fines for invoicing failures. Penalties for failing to issue a CFDI or issuing one that does not meet the required specifications can range from roughly MXN $19,700 to MXN $112,650 per infraction, and they can fall on either the issuer or the recipient who tries to use the invalid invoice. Separate fines apply for missing invoice supplements and for undocumented transportation of goods.
Even without a formal penalty, unverified counterparties create friction that costs money. Accounting teams catching an invalid CFDI after payment either write off the deduction or chase the vendor for a corrected version. New vendor payments get held while documentation is fixed, which strains commercial relationships.
The worst outcome is inheriting a counterparty’s 69-B problem. If the SAT determines your vendor was issuing invoices for transactions that never happened, deductions tied to those invoices can be reversed, and the burden to prove the transactions were real shifts to you. A five-minute lookup on the SAT portal, run before the first payment and repeated on a set cadence afterward, is the standard defense.