e.firma SAT Expiry: How to Check and Renew in Time
A practical guide for accountants: where to check the e.firma SAT expiry date, how far ahead to act, and how to track certificates for dozens of clients.
If you manage accounting for several clients in Mexico, you've probably experienced this: a client arrives on April 1st with an urgent need to stamp payroll or invoice their biggest customer — and their e.firma expired three weeks ago. The SAT renewal process takes 3 to 10 business days. The damage is already done.
This article is the guide you wish you'd had before that moment. We explain exactly where to find the expiry date, how much lead time you need, and how to automate tracking when you're managing not one but fifty clients.
What is the e.firma and why does it expire?
The e.firma (formerly FIEL — Advanced Electronic Signature) is the digital certificate issued by Mexico's SAT tax authority to uniquely identify individuals and businesses before the tax authority. It's required to sign annual declarations, refund requests, SAT portal transactions, and in many cases, to issue digital invoices (CFDI).
The SAT issues it with a validity of four years for both individuals and companies. Once expired, all transactions requiring an electronic signature are blocked until the renewal is complete.
Why doesn't it auto-renew?
Where to check the e.firma expiry date
Option 1 — From the SAT portal
Go to sat.gob.mx → CertiSAT Web
Log in with RFC + password or with the e.firma itself. Inside CertiSAT you can see all active certificates associated with the RFC.
Find the certificate with type 'FIEL'
The 'Expiry Date' column shows the exact day. If it appears in red or shows 'Revoked', the certificate is no longer valid.
Download the .cer to confirm
With the .cer file you can open the properties in any certificate viewer and see the same date without accessing the portal.
Option 2 — From Windows, without the portal
If you have the e.firma .cer file at hand, just double-click it. Windows will open the certificate viewer and show the exact "Valid to" date on the General tab.
Option 3 — From AlertaCert (for multiple clients)
If you manage certificates for several clients, checking them one by one on the SAT portal is not scalable. AlertaCert displays all your certificates in a unified dashboard with a visual traffic-light system and sends automatic email alerts at 90, 60, 30, 15, and 7 days before expiry.
How much lead time do you need?
The general rule used by experienced firms: if the certificate expires in under 90 days, start the conversation with the client. If it expires in under 30, book an appointment immediately.
The renewal process, step by step
Route A — Online renewal (no appointment, from home)
Access SAT ID or CertiSAT Web
The holder must log in with their current valid e.firma. If it has already expired, only the in-person route is available.
Generate a new key pair (.key + .req)
Using Certifica (formerly SOLCEDI), the SAT's free tool. The .req file is the certificate request uploaded to the portal.
Upload the .req to the SAT portal
In CertiSAT Web → 'Certificate Request'. The SAT validates and issues the new .cer within minutes.
Download the new .cer
Store it alongside the .key from the previous step. Those two files are the new e.firma. The password is set by the holder.
Route B — In-person renewal (when the certificate has already expired)
Book an appointment at the SAT
From sat.gob.mx → 'Appointments and Services'. In metropolitan areas wait times can be 1–3 weeks during peak periods.
Attend with required documents
Valid INE or passport + CURP + holder's email address + USB drive. The SAT generates the certificate on-site.
Test the new certificate before leaving
Verify that the new .cer and .key open correctly with the assigned password before leaving the SAT office.
Common mistake
Managing e.firma for multiple clients at scale
| Manual tracking (Excel) | Depends on someone updating the file. One data entry error = client unable to invoice. |
| SAT portal (one by one) | Manageable up to ~5 clients. At 40 clients it's ~2 hours just to review. |
| AlertaCert (cloud vault) | Single upload, automatic alerts, traffic-light dashboard. Works equally for 5 or 500 clients. |
Checklist before an e.firma expires
What about CSD?
Frequently asked questions about e.firma expiry
What is the difference between e.firma and FIEL?
They are the same certificate. Mexico's SAT renamed the Firma Electrónica Avanzada (FIEL) as e.firma in 2017. If a client has files labeled "FIEL" or obtained the certificate before that date, it is still fully valid and functions identically to the current e.firma. The file format is unchanged: a .cer and .key pair protected with a password.
Can I renew a client's e.firma on their behalf?
No. The renewal process requires the physical presence of the certificate holder — or the legal representative, in the case of legal entities with notarized authorization. As the accountant, you can prepare the documents, accompany the client, and even generate the technical files (the .key and .req), but you cannot substitute for the taxpayer at the SAT appointment. This applies to both the online and in-person renewal routes.
How do I know if an e.firma has been revoked, not just expired?
A certificate can be revoked before its expiry date if the holder reported it as compromised, if there was a change in legal representative, or if the SAT cancelled it for irregularities. To check the actual status, you can query CertiSAT Web on the SAT portal (which shows the current state) or perform an OCSP check against the SAT's server, which responds in real time whether a certificate is valid or revoked. AlertaCert performs OCSP validation automatically when you upload a certificate and flags it as "revoked" if applicable, regardless of the expiry date.
What if the e.firma expires while the client has a pending annual declaration?
If the e.firma expires while annual declarations are pending, the client will be unable to sign them electronically. The SAT does not accept declarations signed with an expired certificate. In that scenario, the only option is urgent in-person renewal — which in peak periods can take 1–3 weeks just to get an appointment. Annual declarations and refund requests always require a valid e.firma; this is one of the clearest cases where the cost of not acting in advance becomes very concrete.
Can the e.firma be used to sign PDF documents, not just SAT transactions?
Yes. The e.firma has legal validity for signing any electronic document in Mexico, not just SAT filings. Service contracts, fee agreements, corporate resolutions, and powers of attorney can all be signed digitally using a client's e.firma. AlertaCert includes a PDF signing module where the external signer only needs to click a link and upload their .cer and .key files — no account, no app install required.