Mexico RFC and e.firma: A Business Owner's SAT Registration Preparation Guide

In Mexico the RFC identifies taxpayers and the e.firma (advanced electronic signature) is used for many SAT electronic procedures. The route differs for an individual, a legal entity, a representative and a foreign person, and SAT's appointment guidance changes, so the live portal — not a social-media list — is the authority.

Individual or legal entity? Decide before you book

SAT treats persona física (individual) and persona moral (legal entity) differently: who can appear, what powers are required, and whether a legal representative must attend. A representative needs proof of representation exactly as SAT describes it for that case. Booking the wrong appointment type is a common wasted trip.

Matching names, CURP and address across documents

SAT appointments often fail because the name on the RFC request does not character-match the CURP, passport, or entity record, or because address components are abbreviated differently. Prepare identity and address evidence exactly as requested and use the same spelling everywhere. For legal entities, the notarial instrument and powers must align with the SAT request.

Appointment, appearance and what to bring

1. Read the current requirements and appointment instructions on sat.gob.mx for the persona/ entity you are.
2. Book the appointment at the office that actually handles that procedure.
3. Bring the originals SAT lists (typically official ID, CURP where applicable, proof of address, powers/entity documents) and know which copies, if any, are required.
4. Verify the appointment location — modules move and cities can have multiple SAT offices.

e.firma and file custody

The e.firma consists of a certificate and a private key. SAT will not email you a private key — so any message claiming to do so is fraudulent. Store the .key and .cer files in a restricted, backed-up location with recovery and access procedures for the business. Do not email private key material, and log certificate expiry and renewal tasks. Revocation and renewal run through SAT channels.

After SAT registration

Registration is not the end. Invoicing (CFDI), payroll where you have employees, monthly and annual filings, and VAT obligations follow and depend on the regime, activity and domicile. Ask a contador about regime choice and periodic duties rather than inferring from another taxpayer's situation.

Common mistakes

• Booking an appointment with the wrong persona/ entity selection.
• CURP, name or address mismatch across documents.
• Emailing private key material or leaving it on an unencrypted drive.
• Assuming RFC registration replaces municipal or sector permits.

Official source

SAT — Personas. Verify appointment availability, required evidence and key handling on the live page; this is not Mexican tax advice.

Frequently asked question

Q: Is an RFC the same as a business permit? No. Tax registration is one layer; municipal, sector and professional permissions remain separate where they apply.