Mexico’s tax ID, known as the RFC (Registro Federal de Contribuyentes), is an alphanumeric code the Servicio de Administración Tributaria (SAT) assigns to every person and business earning income or conducting financial transactions in the country. Individuals receive a 13-character code; companies get a 12-character version.1OECD. Mexico TIN – Taxpayer Identification Number Without one, you cannot open a bank account, buy property, issue invoices, or receive a legal paycheck in Mexico. Getting the number is straightforward once you know what to bring and what to expect at the SAT office.
Who Has to Register
Anyone earning money or participating in economic activity in Mexico must register for an RFC. That covers salaried employees, freelancers, business owners, landlords collecting rent, and foreigners buying real estate.2Government of Mexico. Inscription at the Federal Taxpayer Registry The obligation comes from Article 27 of the Código Fiscal de la Federación, which requires every taxpayer to register with the SAT and provide identity, address, and fiscal information.3Cámara de Diputados del H. Congreso de la Unión. Código Fiscal de la Federación
The number touches nearly every financial interaction. Employers need it to run payroll and generate the CFDI digital invoices that serve as official tax receipts. Banks require it to open any account. A Notario Público will not finalize a property sale without a valid RFC for both buyer and seller. Importers must have an active RFC in good standing before registering with the Padrón de Importadores. Once issued, the RFC stays with you permanently and links every significant financial movement to your taxpayer profile.
How the Code Is Built
An individual’s 13-character RFC begins with four letters drawn from the person’s name, followed by six digits for the date of birth, and ends with a three-character homoclave (check digits the SAT assigns to prevent duplicates). A company’s 12-character RFC uses three letters from the business name, six digits from the date of incorporation, and a three-character homoclave.1OECD. Mexico TIN – Taxpayer Identification Number Because the code is built from your personal data, it stays the same for life. You will type it into nearly every government and financial form you encounter, so memorize it the way you would a Social Security number.
What to Bring to Your Appointment
Gather these items before you visit a SAT office:
- Your CURP (Clave Única de Registro de Población), Mexico’s general population ID number. Most foreign residents receive one alongside their residency visa, but you can verify or download yours from the government CURP portal. The SAT lists the CURP as the only prerequisite for initiating your RFC file.4Servicio de Administración Tributaria. Inscripción en el RFC
- A government-issued ID. For foreign applicants, that means a valid passport or your temporary or permanent resident card issued by the Instituto Nacional de Migración.
- Proof of address (comprobante de domicilio). A recent utility bill or bank statement showing your name and address works. The SAT accepts documents up to four months old, and they do not need to show a zero balance.5Servicio de Administración Tributaria. Consulta los Documentos Aceptados como Comprobantes de Domicilio
- A USB flash drive, preferably new, so the SAT official can save your e.firma digital signature files during the appointment.
- A Mexican phone number for contact and verification.
Some SAT offices ask temporary residents to bring a short letter explaining why they need the RFC, such as to purchase property or receive rental income. It is not a universal requirement, but writing a one-paragraph letter of intent and bringing it along prevents a wasted trip if the local office insists on one.
Booking the Appointment
All in-person SAT visits require an appointment booked through the official portal at citas.sat.gob.mx. Slots fill quickly in major cities like Mexico City, Guadalajara, and Cancún, so check regularly if nothing shows as available. During scheduling, the system asks for your CURP and basic contact information to create a pre-registration file. Filling this out accurately saves time at the office because the official will already have your data on screen when you arrive.
A basic RFC number can sometimes be generated online without visiting a SAT office, but that process only creates the code itself. It does not give you the e.firma digital signature, which requires in-person biometric capture. Without an e.firma, you cannot issue invoices, file tax returns electronically, or make most changes to your SAT account later. For anyone planning to be economically active in Mexico, handling everything in a single in-person appointment is the approach that actually works.
What Happens at the SAT Office
The appointment follows a predictable sequence. A SAT official first checks your physical documents against the pre-registration data you submitted online, verifying that your name, CURP, and address match across all records. They then enroll your biometrics: ten fingerprints and a high-resolution iris scan, both stored in the federal taxpayer database and permanently linked to your RFC. You also provide a digital signature on an electronic pad, which is compared against the signature on your ID.
After processing, the official generates your e.firma files, a certificate (.cer) and a private key (.key), and saves them onto your USB drive along with a password you create during the session. Guard these files carefully; they function as your legal electronic signature for tax filings, invoice generation, and official correspondence with the SAT.
The session typically wraps up within 30 to 45 minutes. Before you leave, the official prints your Cédula de Identificación Fiscal, a document that displays your RFC, your registered tax regime, and a QR code that anyone can scan to verify your fiscal status.6Servicio de Administración Tributaria. Obtén tu Cédula de Identificación Fiscal You can also download this document later through the SAT portal or mobile app.7Portal de Trámites y Servicios del SAT. Constancia de Situación Fiscal
Protecting Your e.firma
The e.firma is valid for four years from the date of issuance.8Servicio de Administración Tributaria. Renueva el Certificado de tu e.firma Renew before it expires, or within one year after expiration, and you can complete the process entirely online through the SAT portal, provided you still have your .cer, .key, and private key password. Miss that one-year window after expiration and you are back to booking an in-person appointment with full document verification.
Losing your e.firma files is one of the most common headaches expats run into. Once the files are gone, there is no way to recover them remotely. Store copies in at least two secure locations; an encrypted cloud folder and a backup USB drive work well. Treat the private key password the way you would treat a banking PIN. Never share it, and never store it in plain text alongside the key files.
Activating the Buzón Tributario
Every RFC-registered taxpayer has been required since 2020 to activate the Buzón Tributario, the SAT’s electronic notification system.9Government of Mexico. Habilitar el Buzón Tributario es Obligatorio This is how the SAT sends audit notices, compliance requests, and other official correspondence. Failing to activate it is itself an infraction, and you may also miss notifications with hard deadlines that keep running whether you read them or not.
Two groups are exempt: salaried workers earning under 400,000 MXN per year with no other fiscal obligations, and taxpayers whose RFC status is listed as suspended or canceled.9Government of Mexico. Habilitar el Buzón Tributario es Obligatorio Everyone else should activate it immediately after receiving their RFC, either through the SAT website or the SAT Móvil app, by registering an email address and phone number for notifications.
Keeping Your Information Current
When you move, change your line of work, or switch tax regimes, Article 27 of the CFF requires you to notify the SAT. For address changes specifically, the deadline is ten days from the date of the move.3Cámara de Diputados del H. Congreso de la Unión. Código Fiscal de la Federación If the SAT has already initiated an audit against you, the notice must be filed five days before moving, not after.
Ignoring update obligations is penalized under Articles 79 and 80 of the CFF. Fines for failing to report an address change or similar RFC infractions range from 5,070 to 15,200 MXN.10Justia Mexico. Código Fiscal de la Federación Titulo Cuarto Capitulo I Beyond the fine itself, an outdated record can lead to suspended invoicing privileges, which effectively shuts down your ability to do business until you fix it.
RFC for Foreign Property Buyers
Foreign residents with a temporary or permanent visa follow the same registration process. If you hold a temporary resident card, some SAT offices request a brief letter explaining your reason for registration, such as buying property, starting a business, or receiving rental income.
Foreigners buying real estate face an added wrinkle: the notary handling the transaction will not proceed without a valid RFC for the buyer. The requirement also applies to claiming the capital gains tax exemption when you eventually sell a primary residence. Getting the RFC before you start house hunting avoids delays at the closing table, because notaries have no flexibility here.
Non-residents who do not live in Mexico but need to complete a transaction can sometimes obtain an RFC through a legal representative with a power of attorney. That process is more involved and typically requires help from a Mexican accountant or attorney familiar with SAT procedures.
What the RFC Does Not Do
Holding an RFC does not automatically make you a tax resident of Mexico, though the two are closely related. Under Article 9 of the CFF, you are considered a Mexican tax resident if you have established a home (casa habitación) in the country. If you maintain homes in both Mexico and another country, the tiebreaker is your “center of vital interests,” which Mexico defines as the country where more than 50% of your income originates, or where your primary professional activity is based. Mexican tax residents owe income tax on their worldwide income, not just Mexican-source earnings.
If you are a U.S. citizen or green card holder, having an RFC and Mexican accounts does not replace your U.S. filing obligations. You continue to file U.S. tax returns, and Mexican bank accounts opened with your RFC may trigger separate reporting on FinCEN Form 114 (FBAR) if your combined foreign account balances exceed 10,000 USD at any point during the year.11Internal Revenue Service. Report of Foreign Bank and Financial Accounts (FBAR) The U.S.-Mexico income tax treaty provides relief through a foreign tax credit mechanism, so income tax paid to Mexico can generally be credited against your U.S. tax liability on the same income.12Internal Revenue Service. United States – Mexico Income Tax Convention