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CFDI stamping system: ultra-fast, valid with the SAT.

What invoice stamping is, what a PAC does when it certifies your CFDI, and how you stamp with Factura Digital, in the web app or through the API, with stamps that never expire.

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Summary

Stamping is the step in which an authorized certification provider (PAC) validates your CFDI, assigns its fiscal folio (UUID) and adds the SAT digital seal. Without that stamp, the invoice has no tax validity. A stamping system is the software that builds the XML, sends it for stamping and returns the stamped CFDI to you. At Factura Digital stamping is ultra-fast, valid with the SAT and backed up: if a PAC doesn't respond, your CFDI still gets stamped.

What CFDI stamping is

Stamping means certifying a CFDI (Comprobante Fiscal Digital por Internet, Mexico's electronic invoice). Articles 29 and 29 Bis of the Federal Tax Code (CFF) reserve that certification for the SAT or a provider the SAT authorizes, the PAC. Certifying covers three acts: validating that the invoice meets the tax requirements, assigning a fiscal folio and adding the SAT digital seal.

An invoice counts as issued when, besides being generated and sealed with your Digital Seal Certificate (CSD), it gets the stamp. Before that it's just an XML file with no tax validity, and the SAT has no record of it.

There is a deadline: the CFDI must be stamped within 72 hours of its generation date (rule 2.7.2.9 of the 2026 Miscellaneous Tax Resolution, RMF). After that, the PAC rejects it and it has to be generated again.

What the stamp adds to the XML
UUID
The fiscal folio: 36 characters that identify the CFDI with the SAT.
FechaTimbrado
Date and time the PAC certified the invoice.
SelloCFD
The issuer's digital seal, as it came in the invoice.
NoCertificadoSAT
The number of the SAT certificate used to seal the stamp.
SelloSAT
The SAT digital seal.
RfcProvCertif
The RFC (tax ID) of the certification provider that stamped it.

What a PAC does when it stamps your invoice

The PAC receives the XML already sealed with your CSD and, before stamping it, checks that it meets the SAT rules. If something fails, it rejects it with an error code and the invoice isn't stamped.

  1. 01

    It receives the sealed XML

    The invoicing system builds the CFDI 4.0 according to Annex 20 and seals it with your CSD. That XML is what reaches the PAC.

  2. 02

    It validates the invoice

    It checks the Annex 20 structure and any complements, that your CSD is valid, that the recipient's RFC is on the SAT's list, that it hasn't stamped that invoice before, and that no more than 72 hours have passed since its generation date.

  3. 03

    It assigns the fiscal folio and seals

    It adds the Timbre Fiscal Digital complement with the UUID, the certification date and the SAT digital seal.

  4. 04

    It sends a copy to the SAT

    The PAC sends the CFDI to the SAT when it certifies it (rule 2.7.2.8, RMF 2026) and returns the stamped XML so you can deliver it to your customer.

The guide What is a PAC explains how to check the SAT's list to confirm a provider is authorized, what you get with a direct PAC, and what happens if a PAC loses its authorization.

Read the guide What is a PAC

What a stamping system is

A stamping system is the software that sends your CFDI to a PAC for stamping and returns the invoice, valid with the SAT. In practice it is almost always part of an invoicing system: you enter the data, the system builds the XML with the SAT catalogs, seals it with your CSD, stamps it and gives you the XML and the PDF.

The difference from a direct PAC is how much of the process you handle. With a direct PAC, your team generates and seals the XML and only buys the certification. With a stamping system, the system does that work and stamping is included.

See “Sistema de timbrado” in the glossary

What to check in a stamping system

  1. 01

    Backup if a PAC doesn't respond

    Without backup, your invoice waits until the PAC is back. Ask whether the system can stamp with another PAC.

  2. 02

    Stamp expiration

    Some packages expire or are lost if you don't use them within the month. Check whether your stamps expire.

  3. 03

    API cost

    If you'll stamp from your ERP or online store, check whether the API is billed separately or you only pay for stamps.

  4. 04

    Cancellation

    Check whether cancelling uses a stamp and whether the system gives you the SAT acknowledgment.

  5. 05

    Storage

    A PAC is only required to keep your CFDIs for three months (rule 2.7.2.8, RMF 2026). Check how many years the system keeps your XML and PDF files.

Stamping at Factura Digital

Ultra-fast stamping, valid with the SAT, in the web app and through the API. More than 100 million documents issued since 2008.

Ultra-fast, valid with the SAT

Stamp with a SAT-authorized PAC the moment you issue, from your browser or phone.

Backed up

Ultra-fast PAC stamping with backup: if a PAC doesn't respond, your CFDI still gets stamped.

Stamps that never expire

Each stamped CFDI uses one stamp. The stamps you buy have no expiration date: use them when you need them.

Included in web and API

Stamp in the web app or from your own system with API v5. The API isn't billed separately: you pay for stamps.

Cancelling doesn't use a stamp

Cancel with reasons 01 to 04 and check the status with the SAT without using stamps.

5-year storage

Your XML and PDF files are stored for 5 years.

Stamp from the web app or from your own system

Web app

Invoices on screen

Enter the invoice in your browser or on your phone, with nothing to install. Once it's stamped, copy the UUID, download the XML and PDF, or send them to your customer by email or WhatsApp.

See web invoicing
API v5

Stamp from your own system

Send the data as JSON to the REST API and get back the stamped CFDI in XML and PDF. There's a free sandbox for testing, plus webhooks and SDKs.

See the stamping API

Either way you pay for stamps, and when you sign up you get 10 free, one time only, no credit card. See pricing

Frequently asked questions about stamping

What is invoice stamping?

It is the certification of a CFDI by an authorized certification provider (PAC) or by the SAT. When stamping, the PAC validates the invoice, assigns its fiscal folio (UUID), adds the SAT digital seal and sends a copy to the SAT. Without the stamp, the invoice has no tax validity.

What is a stamping system?

It's the software that sends your CFDI to a PAC for stamping and returns the invoice with its fiscal folio (UUID). It's usually part of an invoicing system, which also builds the XML, seals it with your CSD and delivers the XML and PDF to your customer.

What's the difference between a PAC and a stamping system?

The PAC is the company the SAT authorizes to certify CFDIs. The stamping system is the software that prepares the invoice and sends it for stamping. With a direct PAC your team generates and seals the XML; with a stamping system, the system does it for you and stamping is included.

How long do I have to stamp a CFDI?

Within 72 hours of its generation date (rule 2.7.2.9, RMF 2026). After that, the PAC rejects the invoice and it has to be generated again with a current date.

What happens if the PAC doesn't respond when I stamp?

The CFDI isn't stamped until there is a response, which is why a system with backup helps. At Factura Digital, PAC stamping is ultra-fast with backup: if a PAC doesn't respond, your CFDI still gets stamped.

Do stamps expire?

Not at Factura Digital. The stamps you buy have no expiration date, and each stamped CFDI uses one. Premium is an optional subscription: you don't need it to stamp.

Can I stamp through the API?

Yes. Factura Digital's API v5 is included: you don't pay for the API, you pay for stamps. Send the data as JSON and get back the stamped CFDI in XML and PDF. You can try it for free in the sandbox.

Does cancelling an invoice use a stamp?

No. At Factura Digital cancelling doesn't use a stamp. You cancel with the reasons 01 to 04 the SAT requires and can check the invoice status with the SAT.

How do I know if my invoice is stamped?

Open the XML and look for the TimbreFiscalDigital complement: it holds the fiscal folio (UUID), the stamping date and the SAT seal. You can also look up the invoice by its fiscal folio in the SAT's CFDI verification service.

How much does it cost to stamp an invoice?

It depends on the stamp package: with VAT included, they range from 10 stamps for $120 MXN to 10,000 stamps for $12,000 MXN, and they never expire. Each stamped CFDI uses one stamp; cancelling doesn't use one. When you sign up you get 10 free stamps, one time only, no credit card. The guide How much invoicing costs compares the most common pricing models.

Keep reading

Stamp your first invoice with 10 free stamps.

One time only, no credit card. The stamps you buy afterwards never expire.

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