What are the RFC and e.firma, and how does a foreign company get them?
The RFC is the tax ID the SAT assigns to each taxpayer, and the e.firma is the SAT-issued digital certificate that signs tax filings in place of a handwritten signature. A Mexican subsidiary or a foreign company with or without a permanent establishment can enroll in the RFC, then request the e.firma through a legal representative who is already in the RFC, at a SAT office with an appointment.
RFC and e.firma: what are they for?
The RFC (Registro Federal de Contribuyentes) is the tax registry. The SAT assigns each taxpayer who enrolls a key, delivered through the tax identification card (cédula de identificación fiscal) or the registration certificate (CFF art. 27, C, VIII). For a company, the enrollment receipt (acuse único) carries the card and a QR code and, according to the SAT, shows the tax regime and obligations assigned from the answers to the economic-activity questionnaire (SAT). A company key has 12 characters; an individual's has 13 (SAT, e.firma page).
The e.firma is the SAT's advanced electronic signature. The Código Fiscal requires documents that tax rules demand to be digital and signed with it, and a valid e.firma replaces the handwritten signature and carries the same evidentiary value (CFF art. 17-D). Companies also need it to issue invoices: the taxpayer must hold a valid e.firma and request a digital-seal certificate from the SAT (CFF art. 29). The SAT also assigns a tax mailbox (buzón tributario) to every taxpayer in the RFC, which must be checked within three business days (CFF art. 12 excludes weekends and listed holidays) of an electronic notice (CFF arts. 12, 17-K).
In practice the RFC comes first and the e.firma second. For what each unlocks in an import business, such as the importers' register, see our guide on entering Mexico with or without a company and the company registration process.
Which one does your situation need?
It depends on who will appear on the paperwork. The table summarizes what the SAT pages and the Código Fiscal say; your accountant or lawyer should confirm which case applies.
| Situation | RFC | e.firma |
|---|---|---|
| New Mexican company (S.A. de C.V., S. de R.L. de C.V.) | Its own RFC, through a notary in the remote scheme or at a SAT office ({{c1_sat_fed|SAT}}; {{c1_sat_rfc|SAT}}) | Requested by its legal representative at a SAT office ({{c1_sat_efirma|SAT}}) |
| Foreign shareholder of a Mexican company, not required to register | No own RFC: the company uses the SAT generic code and files an annual list of such shareholders within three months after year-end ({{c1_cff|CFF art. 27}}; {{c1_sat_fed|SAT}}) | The pages we read ask for none for this status |
| Foreign company, with or without a permanent establishment | Its own RFC through a legal representative already in the RFC ({{c1_sat_ext|SAT}}) | Yes, through the same representative, with a section for foreign companies ({{c1_sat_efirma|SAT}}) |
| Foreign individual acting as legal representative | Own individual RFC: a CURP or, for foreigners, a valid migration document, proof of address and ID ({{c1_sat_f39|SAT, sheet 39}}) | Required before the representative can request the company's ({{c1_sat_efirma|SAT}}) |
How does a company enroll in the RFC?
A new Mexican company
Decide who will attend
The legal representative must hold a notarial power for acts of administration or ownership (the SAT requirements also accept a letter of authority signed before two witnesses and ratified), show a valid official ID (a foreigner may present a valid migration document) and already be registered in the RFC (SAT).
Choose the route
Either the notary enrolled in the SAT's remote scheme submits the application at the moment the deed is signed, or the representative does it at a SAT office. In any case, within the month after signing the parties must prove to the notary that the RFC application was filed; if they do not, the notary must report the omission to the SAT within the following month (SAT; CFF art. 27, B, VIII).
Pre-register online if you want
The SAT portal accepts a pre-registration, but it counts as filed only if you finish at a SAT office within ten days (SAT, sheet 43).
Bring the documents
A certified copy of the deed, proof of address (for example a bank statement, utility bill or lease, with the age limits the SAT lists), the representative's power and ID, and the RFC of each partner or shareholder, or a written statement with them (SAT).
Collect the receipt
You receive the application and the single enrollment receipt with the tax card and QR code (SAT). The deadline is the month after the company must first file returns or issue invoices.
A foreign company
The SAT's page for companies resident abroad covers entities with or without a permanent establishment. It is done in person through the legal representative, with an appointment booked on the SAT portal, SAT Móvil or the GOB.MX portal; the SAT states a limit of 40 minutes and no fee, and the deadline is the month after the company must file returns or issue invoices (SAT). The documents it lists are a certified copy of the constitutive document, apostilled or legalized and translated when not in Spanish; the company's foreign tax ID document, as a certified copy, legalized or apostilled, if its country requires one; the document approving a Mexican establishment, if there is one; the representative's power of attorney and ID; the partners' RFC or the generic codes; and proof of address in the name of the company or of a partner.
How does a company obtain its e.firma?
The e.firma of a company can only be requested by a representative who holds, before a notary, a general power for acts of ownership or administration, and who already has a valid e.firma of their own (CFF art. 19-A). The SAT page adds that the appointment is booked in advance, that the procedure is free, and that the representative is the one who attends.
Check the conditions
The representative is registered in the RFC and holds an e.firma; the company has an email account and an updated tax domicile; and the application form is signed in blue ink, in duplicate (SAT).
Book the appointment
On citas.sat.gob.mx, the SAT portal or SAT Móvil, at an office that offers e.firma service for companies (SAT; sheet 105/CFF).
Bring the file
A USB drive, preferably new; the deed (original or certified copy); the power; the representative's ID; proof of address in the company's name; the updated list of partners; and a written statement naming the shareholder with effective control (SAT).
Attend in person
The SAT takes fingerprints, a front photo, an iris photo and the signature, and scans the originals (SAT).
Receive the certificate or the request
If approved, you receive the certificate (.cer file) and the generation receipt. If not, you receive a receipt asking for information, answered by a clarification the SAT reviews within 10 days (SAT).
The SAT will refuse the certificate when the company has a controlling partner or shareholder who is in certain situations listed in the Código Fiscal and has not corrected their tax status (CFF art. 17-D). A certificate lasts four years at most, and a new one can be requested before it ends (art. 17-D).
What do the documents from China need?
The SAT pages repeat the same rule for foreign documents: a document issued abroad must be apostilled or legalized, formalized before a Mexican notary and, if it is not in Spanish, translated by an authorized translator. This applies to the constitutive document, the document recording the decision to open a Mexican establishment, the foreign tax ID document and a power of attorney granted outside Mexico (SAT; SAT).
The HCCH status table lists China as a party to the Apostille Convention in force from 7 November 2023 and Mexico from 14 August 1995 (HCCH). Whether an apostille or a consular legalization is the right route for each document, and who translates it, should be confirmed by the Mexican notary before the papers are signed, because a document that does not meet the SAT requirements may be rejected.
Keep the company's data consistent across the documents: legal name, address, shareholders, the person who will represent it. The SAT checks the identity, domicile and tax situation declared and may refuse the e.firma if it cannot validate them (CFF art. 17-D).
What should you do next, and who should you ask?
Before you book anything, ask your Mexican lawyer or accountant three questions in writing: which of the cases in the table is yours, who will be the legal representative and does that person already have an RFC and e.firma, and what is the quote and what does it include. We found no official source for professional fees, and the e.firma page gives no processing time.
Xin Puente connects Chinese companies with independent licensed Mexican partners and coordinates in Chinese; we are not a law firm, notary or accounting firm, and you contract and pay them directly. When you are ready to compare options, the free assessment is a no-pressure place to start, and our guide on verifying Mexican professionals shows how to check whoever you hire.
Verified 26 Oct 2026 against: Código Fiscal de la Federación, SAT (RFC de empresas), SAT (ficha 43/CFF), SAT (fedatario, medios remotos), SAT (RFC de empresa residente en el extranjero), SAT (ficha 39/CFF), SAT (e.firma de empresas), SAT (ficha 105/CFF), HCCH (Convenio Apostilla).
Frequently asked questions
Does a foreign company need its own RFC to hold shares in a Mexican company?
Not necessarily. Foreign partners of a Mexican company are not obliged to register if the company files, within the first three months after each year-end, a list with their address, tax residence and foreign tax ID number; the SAT provides generic codes for them (CFF art. 27; SAT). Whether this applies to your structure is a question for your accountant.
Can the RFC and e.firma be obtained online?
Only in part. The SAT portal accepts a pre-registration for a new company, but it counts only if you finish at a SAT office within ten days (SAT, sheet 43). The foreign-company page says the enrollment is in person, and the e.firma needs an in-person visit with biometric data (SAT; SAT).
How long is an e.firma valid?
For tax purposes a certificate lasts at most four years from its issue, and the holder can request a new one before it ends (CFF art. 17-D).
Does the SAT charge for these procedures?
The SAT pages we read list the RFC enrollment of companies, of foreign companies and the company e.firma as free (SAT; SAT; SAT). Notary, translation, apostille and professional fees are separate and we found no official figure.
What if the SAT does not issue the e.firma?
You receive a receipt asking for more information about the company's tax situation; you answer with a clarification that the authority reviews within 10 days, and the SAT will deny the certificate in the cases listed in the Código Fiscal (SAT; CFF art. 17-D). A Mexican accountant should handle the response.
What does Xin Puente do in this process?
We introduce Chinese companies to independent licensed Mexican partners and coordinate in Chinese. We are not a law firm, notary, accountant or customs broker and do not give legal, tax or customs advice. You contract and pay the professionals directly.
Sources
- Cámara de Diputados: Código Fiscal de la Federación (texto vigente, última reforma DOF 09-04-2026)
- SAT: Inscribe tu empresa en el RFC (trámite)
- SAT: Inscripción en el RFC de personas morales (ficha 43/CFF)
- SAT: Inscripción en el RFC de personas morales a través de fedatario público por medios remotos (ficha 45/CFF)
- SAT: Inscribe una empresa u organismo residente en el extranjero en el RFC (trámite)
- SAT: Solicitud de inscripción en el RFC de personas físicas (ficha 39/CFF)
- SAT: Obtén el certificado de e.firma para tu empresa (trámite)
- SAT: Solicitud del certificado de e.firma (ficha 105/CFF)
- Conferencia de La Haya de Derecho Internacional Privado (HCCH): Convenio Apostilla, tabla de estatus (Convention #12)
Rules and figures change. Before you decide, check the official sources and confirm with a licensed professional.
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