Written for Mexico. This analysis applies to Mexican federal tax law — ISR (income tax), IVA (VAT) and SAT rules — and cites Mexican statutes. Amounts are in Mexican pesos (MXN).
To issue a CFDI in any invoicing software (your accountant's, your ERP, or a commercial one) you need a Digital Seal Certificate (Certificado de Sello Digital) — the cryptographic "seal" that signs each invoice. It's a 100% online procedure, free and a single afternoon's work… if you know it's two separate applications and which order they go in. Here's the exact map, including the detail that confuses everyone: the software is called Certifica — it's the successor to the old SOLCEDI, which many tutorials still refer to by its former name.
Before you start: what it is (and what you need)
The CSD is a pair of files (.cer + .key with a password) issued by the SAT exclusively to seal invoices — not to be confused with the e.firma, which is your general legal identity and is, moreover, the prerequisite: with no valid e.firma there is no CSD. You'll need: your e.firma files (.cer, .key and password), a computer with the SAT's Certifica application installed (official download, 32/64-bit version depending on your machine), and a new, well-named folder where the seal files will live — certificate disorganization is the number-one source of "I can't invoice" at 11 pm on the 17th. Practical note: individuals can invoice without a CSD by using their e.firma in the SAT's free tool ("Genera tu factura") — enough for small volumes; to invoice seriously (systems, volume, branches), the CSD is the way to go.
The process in two acts
Act 1 — Certifica (on your computer): open the application and choose "Solicitud de Certificado de Sello Digital" (Digital Seal Certificate request). Load your e.firma's .cer, name the branch or unit (if you don't have one, your business name or "matriz"/headquarters works), and set the private-key password for the seal — write it into your password manager right then: there is no "recover password," only generating a new seal. The program will ask you to move the mouse to generate randomness, you'll sign with your e.firma .key, and at the end you'll have two files: the CSD .key and a .sdg request file. Act 2 — CertiSAT Web (in the browser): log in with your e.firma, choose "Envío de solicitud de certificados de sello digital" (submit digital seal certificate requests), upload the .sdg and save the operation number. The SAT processes and issues your certificate: the seal's .cer is downloaded from the "Recuperación de certificados" (Certificate Recovery) section — the same certificate lookup portal — searching by your RFC for the most recent certificate of the SELLO (seal) type. Timing: issuance usually takes minutes to hours, and bear in mind that the seal can take up to 72 hours to become active for stamping — don't generate the CSD the same day you need your first invoice. With .cer + .key + password loaded into your invoicing software, you're issuing.
The operating rules nobody tells you
One seal per unit: you can (and in serious structures, you should) generate separate CSDs per branch or per system — if one point is compromised, you revoke that seal without shutting down the whole operation. Custody = control of your invoicing: whoever holds your .key and password can issue CFDIs in your name; the seals are handed to providers and accountants under protocol (and revoked when the relationship ends — the annual certificate audit exists for this). Validity 4 years, with online renewal as long as your e.firma lives. And the underlying warning: the CSD is also the switch the SAT can turn off — articles 17-H and 17-H Bis of the CFF allow it to temporarily restrict or void your seals for grounds such as failing to file returns, not being locatable at your registered address, or presumptions of nonexistent transactions. Invoicing halted = business halted: it's the authority's most effective pressure lever, and the reason the "minor" obligations (zero returns included, the tax mailbox, a locatable address) are not optional.
Just starting to invoice — or does your operation depend on seals you don't control?
We set up the full launch (CSD per unit, custody protocol, the right invoicing software for your case) or audit the existing one: seal inventory, pending revocations, and the traffic-light review of the 17-H Bis grounds that could be pointing at you. A seal restriction is prevented in one session; reversing it takes weeks of clarifications with the operation on hold.
Frequently asked questions
So SOLCEDI no longer exists?
Correct — SOLCEDI was the legacy application and today the official software is called Certifica (same purpose: generating the e.firma and CSD request files on your computer). If a tutorial or your accountant says 'SOLCEDI,' read it as Certifica. Submitting the requests, in both cases, is completed in CertiSAT Web.
Can I use my e.firma directly in the invoicing tool instead of the CSD?
In the SAT's free tool, individuals can stamp with their e.firma. In commercial invoicing software and systems, the standard is the CSD — and it's best practice in any case: it puts a limited certificate (one that only invoices) at risk instead of your full legal identity. The e.firma is never shared with anyone, ever; the CSD is shared under protocol.
I generated my CSD and the invoicing software says 'invalid certificate' — what should I check?
The usual three suspects: (1) activation pending — wait the required hours; (2) you're loading the e.firma files instead of the seal files (or mixing the .cer of one with the .key of the other — they must be a pair); (3) wrong private-key password. If everything checks out and it persists, verify the seal's status in Certificate Recovery: it could be revoked or restricted.
How often should I rotate the seals even if they haven't expired?
There's no obligation to rotate, but there are good practices triggered by events: a change of accountant or invoicing provider, staff with access leaving, any suspicion of a leak. Revoking and regenerating takes an afternoon and is free — a bogus invoice issued with your legitimate seal, by contrast, is a serious evidentiary problem: the CFDI went out signed by 'you.'
Let's talk about your case
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