Untangling CFDI: What Is a PAC?

Understanding Their Role in Mexico’s E-Invoicing System

Part of the “Untangling CFDI” Series

If you’re issuing invoices in Mexico, chances are you’ve heard the term PAC. But what exactly is a PAC, and why does it matter for your business?

PACs (Proveedores Autorizados de Certificación) play a central role in Mexico’s electronic invoicing infrastructure. This post breaks down what PACs are, why they exist, their limitations, and what to consider when choosing a provider—so you can stay compliant and streamline your digital tax operations.

What Is a PAC?

A PAC is an officially authorized certification provider recognized by Mexico’s tax authority (SAT). In simple terms, PACs act as the bridge between your business and the SAT.

They validate and stamp your CFDIs, making your electronic invoices legal and tax-compliant. Think of a PAC like a digital notary that ensures your invoice is properly formatted, time-stamped, and registered with the SAT.

Why Does Mexico Use PACs?

The SAT requires that all electronic invoices be processed through a PAC in order to:

• Ensure data integrity
• Validate tax compliance in real time
• Enable traceability for audits and legal transparency

This system helps fight fraud and gives the SAT access to real-time transactional data from millions of businesses across the country.

How Does a PAC Work?

Here’s a simplified breakdown of how PACs interact with your invoicing system:

1. You generate an invoice using your ERP, billing system, or API.
2. You send the invoice to a PAC.
3. The PAC validates it, applies a digital signature, adds a timestamp, and sends it to the SAT.
4. The SAT confirms receipt, and your invoice is now valid for tax purposes.

What Should You Look for in a PAC?

Not all PACs are the same. Whether you’re working through an ERP, billing platform, or API, here are five key criteria to consider:

1. SAT Authorization
2. Always confirm the PAC is officially listed by the SAT. Using an unauthorized provider can expose you to legal risk.
3. Availability + Uptime
4. PACs must be operational at all times. If your PAC goes down, so does your invoicing—and potentially your cash flow.
5. Scalability
6. Your needs may be simple now, but will your PAC support high-volume, low-latency processing as you grow?
7. Developer Experience
8. If you’re integrating with your own software, solid documentation and dev tools are essential. Look for sandbox access, clean SDKs, and responsive support.
9. CFDI 4.0 Compliance
10. The SAT frequently updates its invoicing rules. A modern PAC keeps up to date to help you avoid errors and rejections.

Limitations of PACs

While PACs are essential for legal compliance, many weren’t built with modern digital business needs in mind. Most were created as basic compliance tools—not full digital tax platforms—leaving significant gaps for today’s tech-forward companies.

Some common limitations of PACs include:

• Slower processing times during peak periods
• No invoice creation, management, or analytics tools—just stamping
• Clunky or outdated user interfaces
• Lack of automation, error handling, multichannel delivery, or real-time reporting
• Limited scalability for growing businesses or digital-native expectations

Fortunately, a new category of tools builds on top of traditional PACs to deliver a modern interface and enhanced value-added services. We’ll dive deeper into this topic in our next article: “Value-Added PACs: The CFDI Service Providers for Digital-Native Businesses”.

Frequently Asked Questions

Do I need a PAC to issue CFDIs?

Not directly. You can either work with a PAC or choose a modern solution like Facturapi, which acts as a front-end to a PAC—offering faster processing, a user-friendly interface, better reporting, and additional services built for digital-first businesses.

Do international businesses need a PAC?

Yes—if they operate in Mexico. They’ll need a PAC or a PAC+ solution like Facturapi to handle CFDI compliance.

What other services do PACs offer?

Typically, none beyond CFDI stamping. That’s a major limitation. You may want to consider “PAC+” providers like Facturapi, which also offer manual CFDI processing, modern dashboards, 3rd-party integrations (e.g., Stripe), CFDI synchronization, e-invoicing, and more.

Final Thoughts

PACs are the foundation of Mexico’s CFDI system. But as business needs evolve, so should the tools that support them. Traditional PACs might work for legacy businesses with time and resources to manage invoicing manually. For modern, fast-growing companies, an API-driven solution is often a better fit.

Our “Untangling CFDI” series explores these themes in more depth. Be sure to check out the next post: “Value-Added PACs: The CFDI Service Providers for Digital-Native Businesses.”