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What is a PAC in Mexican invoicing and how to choose one.

What a certification provider does when it stamps your CFDI, how to check that it is authorized by the SAT, what you buy with a direct PAC versus an invoicing system, and what happens if a PAC fails.

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By the Factura Digital TeamPublished September 28, 2026~12 min read
Summary

A PAC (Proveedor Autorizado de Certificación, an authorized certification provider) is a company authorized by the SAT to stamp CFDIs: it validates the invoice, assigns the fiscal folio (UUID), adds the SAT digital seal, and sends a copy to the SAT. Without a stamp, a CFDI has no tax validity. Before you sign up, look up the provider's name and RFC on the SAT's official list.

What a PAC is

PAC stands for Proveedor Autorizado de Certificación, an authorized certification provider. The Miscellaneous Tax Resolution (RMF) calls it a CFDI certification provider. It is a company the SAT authorizes to certify CFDIs (Mexico's electronic invoices), based on articles 29 and 29 Bis of the Federal Tax Code (CFF).

Certifying, or stamping, covers three acts the law reserves for the SAT or whoever it authorizes: validating that the invoice meets the tax requirements, assigning it a folio, and adding the SAT digital seal. A CFDI is considered issued when, besides being generated and sealed with your CSD, it gets that stamp.

The authorization isn't permanent. To get it and keep it, each PAC meets requirements in the 2026 RMF, including:

Capital
Subscribed and paid-in capital of at least MXN 10 million (rule 2.7.2.8, section II).
Guarantee
A guarantee that backs its obligations to validate CFDIs and send them to the SAT (rule 2.7.2.6).
Audits
SAT reviews, at any time, of information security, confidentiality, and availability (rule 2.7.2.10).
Term
Two fiscal years, renewable for two more if it meets the requirements (rules 2.7.2.3 and 2.7.2.4).
Free application
A free application to generate and certify CFDIs, available to the public (rule 2.7.2.8, section VII).

What a PAC does when it stamps your CFDI

Stamping takes seconds, but several validations happen inside. This is the path of a CFDI 4.0:

  1. 01

    You generate the XML

    The invoice is built as a version 4.0 XML following Annex 20: issuer, receiver, line items, taxes and, where applicable, complements such as Payments, Payroll, or Carta Porte.

  2. 02

    You seal it with your CSD

    The issuer's digital seal is computed with your Digital Seal Certificate (CSD), issued by the SAT. It proves the invoice came from your RFC and that nobody altered it afterwards.

  3. 03

    The PAC validates it

    It checks the Annex 20 structure, the requirements of CFF article 29-A and of the complements, that your CSD was valid and not revoked, that the receiver's RFC is on the SAT's RFC list, that the same provider hasn't stamped it before, and that no more than 72 hours have passed since its generation date (rule 2.7.2.9).

  4. 04

    It assigns the fiscal folio and seals

    If everything passes, it adds the Timbre Fiscal Digital complement: fiscal folio (UUID), certification date and time, CFDI seal, SAT certificate number, and SAT digital seal.

  5. 05

    It sends a copy to the SAT and returns the CFDI

    The PAC sends the CFDI to the SAT at the moment of certification (rule 2.7.2.8, section IX) and returns the stamped XML to you. If something fails, it rejects it with an error code and the invoice isn't stamped.

  6. 06

    You deliver the CFDI to your customer

    You send the XML and, if requested, the PDF, which is its printed representation (CFF article 29, section V).

Example with sample data
<tfd:TimbreFiscalDigital
  Version="1.1"
  UUID="5FB2822E-396D-4725-8521-CDC4BDD20CCF"
  FechaTimbrado="2026-09-28T10:42:17"
  RfcProvCertif="AAA010101AAA"
  SelloCFD="kXzL9…Q2w=="
  NoCertificadoSAT="30001000000500003456"
  SelloSAT="Hm7Rt…wA4="
/>
RfcProvCertif is the RFC of the certification provider that stamped the invoice. Use it to look the provider up on the SAT list.

How to check that a PAC is authorized

The SAT publishes the official list of authorized providers. We don't copy it here because it changes with every new authorization, revocation, or renewal: check it directly on the SAT portal.

Open the SAT list
  1. 01

    Look up the name or RFC

    For each provider, the list shows its logo, legal name, RFC, and SAT certificate number (rule 2.7.2.2). The brand name may not match the legal name: compare the RFC.

  2. 02

    Check the removals

    On the same portal the SAT publishes providers whose authorization was revoked, not renewed, or withdrawn, within five days of each case.

  3. 03

    Compare with a stamped CFDI

    Open the XML of an invoice stamped by that provider and find RfcProvCertif in the Timbre Fiscal Digital. It must be the RFC of an authorized PAC. If you use an invoicing system, the same field appears in every XML.

  4. 04

    Verify the invoice with the SAT

    The SAT's CFDI verification service confirms with the fiscal folio that the invoice exists and shows its status.

  5. 05

    Don't rely on the logo

    Each PAC must display on its website the logo the SAT gives it upon authorization (rule 2.7.2.8, section XXI). A logo without the RFC on the list proves nothing.

Direct PAC or invoicing system: what you buy in each case

To stamp you need an authorized PAC. The decision is how much of the process you handle yourself. With a direct PAC you buy certification; with an invoicing system you buy the whole process, and stamping is included.

Direct PACInvoicing system
What you pay forDirect PACStamps, in packages or by volume, and access to the stamping service, usually a web service.Invoicing systemStamps or a subscription that covers data entry, stamping, delivery, cancellation, and reports.
Who builds the XMLDirect PACYour team or your ERP: you generate the Annex 20 XML and seal it with your CSD.Invoicing systemThe system, from the data you enter on screen or send through the API.
IntegrationDirect PACYou build and maintain it: connection, error handling, retries, and testing.Invoicing systemIncluded. On screen, or through the API: you send the data and get the stamped CFDI back.
SAT changesDirect PACYour team updates catalogs, complements, and validations when the SAT publishes them.Invoicing systemThe provider updates the system.
If the PAC doesn't respondDirect PACYour integration decides: wait, retry, or send to a second PAC if you have one.Invoicing systemDepends on the provider. Some stamp with backup on another PAC.
StorageDirect PACIt's on you. The PAC is only required to keep CFDIs for three months (rule 2.7.2.8, section XII).Invoicing systemDepends on the provider: check how many years it keeps your XML and PDF files and how you download them.
Best forDirect PACCompanies with an engineering team, their own ERP, and high volume.Invoicing systemIndividuals, SMBs, accountants, and companies that would rather not maintain the integration.

Some companies are PACs and also sell a system, and some systems stamp with one or more PACs. For your customer, the CFDI is worth the same: what changes is how much work and operational risk you take on.

If you are adding invoicing to your product, also compare an invoicing API with a direct PAC integration. With the Factura Digital API you send the JSON and get the stamped CFDI back, ultra-fast and valid with the SAT. To see how backup across several PACs works, read PAC vs. multi-PAC: electronic invoicing architecture.

How much stamping costs

There is no official price: each PAC and each system sets its own. What repeats are the pricing models:

Stamp packages
You prepay a number of stamps. The price per stamp goes down with volume.
Monthly plan with included stamps
You pay a fixed monthly fee for a set number of stamps. The ones you don't use that month are lost.
Packages with an expiry date
You pay once and have a window, for example 12 months, to use them. When it ends, the rest are lost.
Packages that never expire
You pay once and the stamps stay available until you use them.
Volume contract
For high-volume companies: a negotiated price, sometimes with a monthly minimum.

Beyond the stamp, check whether cancellation, users, each additional RFC, the API, or complements cost extra. For simple cases there are two free options: the free application every authorized PAC must offer (rule 2.7.2.8, section VII) and the SAT portal's free invoicing service.

To work out your real cost per invoice by volume, with examples, read How much invoicing costs. Factura Digital prices, VAT included, are on the Pricing page.

What happens if a PAC fails or loses its authorization

If the PAC doesn't respond

While the PAC doesn't respond, your CFDI isn't stamped. There is some room: an invoice can be stamped up to 72 hours after its generation date (rule 2.7.2.9, section I); after that, it has to be generated again. If a PAC plans to suspend its service temporarily, it must notify customers at least 60 days in advance (rule 2.7.2.8, section XIV). And rule 2.7.2.7 allows using one or more PACs at the same time, so a second PAC is a legal option.

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

If the SAT revokes the authorization

Rule 2.7.2.12 sets a 90-calendar-day transition period:

  1. Within 5 days

    The SAT publishes the revocation on its portal within five days after it takes effect (rule 2.7.2.2).

  2. Days 1 to 30

    The PAC keeps stamping for existing customers and can't take new ones. Within three days of publication it must post an URGENT NOTICE (AVISO URGENTE) on its website and email it to all its customers.

  3. Days 31 to 90

    The PAC can no longer stamp. It only closes out its pending obligations with the SAT.

In practice, you have 30 days to switch PACs without interrupting your invoicing.

If it doesn't renew its authorization

The authorization expires at the end of its term. In the last two months, the PAC must notify its customers and stop signing up new ones; from the day after expiry it can no longer stamp (rule 2.7.2.4).

Your CFDIs already stamped

The PAC sends each CFDI to the SAT when it certifies it, and the SAT keeps a copy (rules 2.7.2.8 and 2.7.2.9). You can confirm the status of any invoice with the SAT verification service. Still, keep your XML files: the PAC is only required to keep them for three months, and the CFF requires you to keep your records, as a general rule, for five years (article 30).

What to do if your PAC loses its authorization

  1. 01

    Confirm the publication on the SAT portal and the dates in the PAC's notice.

  2. 02

    Download and back up your XML files and cancellation receipts.

  3. 03

    Sign up with another authorized PAC or an invoicing system and provide the written authorization required by rule 2.7.2.7.

  4. 04

    Update your integration or ERP and test invoices, payment complements, and payroll.

  5. 05

    Tell your team the cutover date.

How to choose a PAC or an invoicing system

Ten things to check before you sign up. They apply equally to a direct PAC and to an invoicing system.

  1. 01

    Current authorization

    The RFC appears on the SAT list as authorized, not on the revoked or non-renewed list.

  2. 02

    Backup

    What happens when the PAC doesn't respond: retries, a second PAC, or just an error message.

  3. 03

    Pricing model

    Price per stamp including VAT, whether stamps expire, and what happens to unused ones.

  4. 04

    Extra charges

    Whether cancellation, users, each additional RFC, the API, or complements cost extra.

  5. 05

    Complements

    Support for the ones you use: Payments 2.0, Payroll 1.2, Carta Porte 3.1, Foreign Trade 2.0.

  6. 06

    Services in writing

    The RMF requires PACs to separate certification from complementary services in contracts and advertising (rule 2.7.2.5, section III). Ask for that detail.

  7. 07

    Storage

    How long your XML and PDF files are kept and how you download them in bulk.

  8. 08

    API and sandbox

    If you'll integrate: public documentation, a free test environment, and clear error codes.

  9. 09

    Support

    Channels, hours, and whether you reach people who know the CFDI.

  10. 10

    Track record

    How many CFDI versions the provider has been through. Every SAT change tests its operation.

Stamping at Factura Digital

Ultra-fast stamping, valid with the SAT

Enter the invoice in the browser, on your phone too, or send the JSON through the API and get the stamped CFDI 4.0 back.

Ultra-fast PAC stamping with backup

If a PAC doesn't respond, your CFDI still gets stamped.

Stamp with a SAT-authorized PAC

Every XML carries its Timbre Fiscal Digital with the fiscal folio (UUID) and the SAT seal.

Stamps that never expire

10 free stamps when you sign up, one time only, no credit card. Premium is an optional subscription.

5 years of storage

Your XML and PDF files are kept for 5 years, with download as XML, PDF, or ZIP.

Since 2008

Operating since 2008, through every CFD and CFDI version up to 4.0. +100 million documents issued.

PAC FAQ

What is a PAC in Mexican e-invoicing?

A PAC (Proveedor Autorizado de Certificación, or authorized certification provider) is a company authorized by the SAT to certify, or stamp, CFDIs. When it stamps, it validates that the invoice meets the tax requirements, assigns the fiscal folio (UUID), adds the SAT digital seal, and sends a copy to the SAT. The legal basis is in articles 29 and 29 Bis of the Federal Tax Code (CFF) and in rules 2.7.2 of the Miscellaneous Tax Resolution (RMF).

What does PAC stand for?

Proveedor Autorizado de Certificación: authorized certification provider. The Miscellaneous Tax Resolution calls it a CFDI certification provider (PCCFDI). In the market, PAC is used for any company the SAT authorizes to stamp.

How do I know if a PAC is authorized by the SAT?

Look up its name or RFC in the List of Authorized Certification Providers on the SAT portal. The list shows each provider's logo, legal name, RFC, and SAT certificate number, and the SAT also publishes providers whose authorization was revoked or not renewed. To confirm with a real invoice, open the stamped XML and compare the RfcProvCertif attribute of the Timbre Fiscal Digital with the RFC on the list.

Do I need to hire a PAC to invoice?

Every CFDI needs a stamp from an authorized PAC or from the SAT itself. You don't have to hire a PAC separately: an invoicing system includes stamping. A direct PAC makes sense when your team generates and seals the XML in its own system and only needs it certified.

What's the difference between a PAC and an invoicing system?

The PAC certifies the invoice: it validates, assigns the fiscal folio, seals, and sends a copy to the SAT. An invoicing system covers the whole process: data entry, catalogs, XML generation, stamping, delivery to the customer, cancellation, and reports. With a direct PAC you pay for stamps and maintain your integration; with a system you pay for the service and stamping is included.

What is a stamping system?

A stamping system is the software that sends your CFDI to an Authorized Certification Provider (PAC) so it validates it and adds the Digital Tax Stamp with its fiscal folio (UUID). Without the stamp, the invoice has no tax validity before the SAT. 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.

How much does it cost to stamp an invoice?

There is no official price. The most common models are stamp packages (with or without expiration), monthly plans with included stamps that are lost if unused, and volume contracts. The price per stamp goes down with volume. In addition, every authorized PAC must offer a free application to generate and certify CFDIs (rule 2.7.2.8, section VII, RMF 2026).

Can I use more than one PAC?

Yes. Rule 2.7.2.7 of the 2026 RMF allows taxpayers to use one or more certification providers at the same time. You must give each one written authorization to deliver to the SAT a copy of the invoices it certifies for you.

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

The CFDI isn't stamped until the PAC responds. An invoice can be stamped up to 72 hours after its generation date (rule 2.7.2.9); after that, it has to be generated again. That's why a second PAC or 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.

What happens to my invoices if my PAC loses its authorization?

The CFDIs it already stamped are with the SAT: the PAC sends each one when it certifies it and the SAT keeps a copy. You can check them with the SAT's CFDI verification service. To keep invoicing, a revocation starts a 90-calendar-day transition: for the first 30 days the PAC keeps stamping for existing customers, and for the next 60 it can no longer stamp (rule 2.7.2.12). Switch providers within those first 30 days.

How long does a PAC's authorization last?

The authorization is valid for the two fiscal years following the one in which it is notified, and the PAC can renew it for two more if it meets the requirements (rules 2.7.2.3 and 2.7.2.4, RMF 2026). If it doesn't renew, it can no longer stamp from the day after it expires.

What data does the PAC add when it stamps?

It adds the Timbre Fiscal Digital complement with the fiscal folio (UUID), the certification date and time, the CFDI digital seal, the SAT certificate number, the SAT digital seal, and the certification provider's RFC (RfcProvCertif).

How does stamping work at Factura Digital?

Ultra-fast stamping, valid with the SAT. It is ultra-fast PAC stamping with backup: if a PAC doesn't respond, your CFDI still gets stamped. When you sign up you get 10 free stamps, one time only, no credit card; the stamps you buy never expire, and Premium is an optional subscription.

Keep reading

Sources

Official regulations and services consulted on September 27, 2026.

  1. List of Authorized CFDI Certification Providers (Spanish)SATAuthorized providers, plus providers whose authorization was revoked, not renewed, or withdrawn.
  2. Federal Tax Code (CFF), articles 29, 29 Bis and 30 (Spanish)Chamber of Deputies (last amended DOF 2026-04-09)What certifying a CFDI means, who may do it, and how long to keep records.
  3. 2026 Miscellaneous Tax Resolution (RMF), rules 2.7.2.1 to 2.7.2.12 (Spanish)SAT (DOF 2025-12-28; text in force with its First Amendment)Requirements, obligations, validations, term and revocation of certification providers.
  4. CFDI verification service (Spanish)SATCheck the status of a CFDI with its fiscal folio (UUID).

Ultra-fast stamping, valid with the SAT.

10 free stamps, one time only, no credit card. You pay for stamps that never expire; Premium is an optional subscription.

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