What is a CFDI and why is it required?
A CFDI is Mexico's structured digital fiscal receipt. Taxpayers required to issue a fiscal invoice use the current CFDI 4.0 XML and obtain its digital tax stamp under the SAT process. Specific CFDI types and complements apply to different transactions.
A correctly issued CFDI is one of the records needed to support tax treatment such as an eligible deduction or IVA credit. The recipient must also satisfy the substantive tax requirements. A receipt, self-designed PDF or spreadsheet does not replace the CFDI.
What roles do SAT and the PAC play?
Two parties sit behind every legitimate CFDI. SAT (Servicio de Administracion Tributaria) is Mexico's federal tax administration. It defines the CFDI standard, publishes the technical schemas and catalogs, and ultimately validates every invoice. A PAC (Proveedor Autorizado de Certificacion, an Authorized Certification Provider) is a private company that SAT has licensed to stamp invoices on its behalf.
The flow works like this: you prepare the invoice data, sign it with your digital certificate, and send the XML to a PAC. The PAC validates the structure, applies the official fiscal stamp, and returns a CFDI carrying a unique UUID (the folio fiscal) that proves SAT has registered it. Only then is the invoice valid. SAT also offers its own free issuing tool through the Factura Electronica portal for low-volume issuers, but most businesses use a PAC or invoicing software connected to one.
- SAT
- The tax authority that sets the CFDI 4.0 standard, maintains the catalogs, and validates and stores every stamped invoice.
- PAC
- A SAT-authorized provider that stamps your XML, applies the fiscal seal, and returns the UUID folio that makes the CFDI valid.
- CSD (digital seal certificate)
- Your Certificado de Sello Digital, issued by SAT, used to sign each invoice so the PAC can verify it is genuinely from you.
- UUID (folio fiscal)
- The unique 36-character identifier SAT assigns to each stamped CFDI. It is the proof the invoice exists in SAT's records.
What are the RFC and Uso del CFDI?
CFDI 4.0 validates prescribed issuer and recipient fields against the current SAT rules. The RFC (Registro Federal de Contribuyentes) is the federal taxpayer registration code. The recipient data normally includes the registered name, RFC, fiscal postal code and tax regime. Special generic RFC rules cover cases such as the general public and foreign recipients.
Uso del CFDI is the SAT catalog code for the recipient's stated fiscal use. It must be compatible with the recipient's tax regime. The customer can obtain its data from SAT records such as the Constancia de Situación Fiscal, but the issuer needs the data itself, not necessarily a paper copy of that certificate.
- Issuer RFC
- Your own taxpayer registration code, tied to the digital seal certificate you sign the invoice with.
- Recipient RFC, name and postal code
- Use the recipient data required by CFDI 4.0 and the applicable generic-recipient rule, if any.
- Regimen Fiscal
- The tax regime code for each party, which also has to match what SAT has registered.
- Uso del CFDI
- A catalog code the buyer selects (for example G03 general expenses) describing how the invoice will be used.
How does a CFDI differ from an ordinary invoice?
It helps to separate two things: the billing document you and your customer read, and the fiscal record SAT validates. In most countries a single PDF does both jobs. In Mexico the fiscal record is the stamped XML, and the PDF is only a human-readable representation of it. The table below shows the difference.
| Aspect | Plain PDF invoice | CFDI 4.0 (Mexico) |
|---|---|---|
| Format | PDF or paper you design | Structured XML in SAT's 4.0 schema |
| Validation | None required | Stamped by a PAC and validated by SAT |
| Unique identifier | Your own invoice number | SAT-assigned UUID (folio fiscal) |
| Tax deductibility | Not deductible on its own | Required for the buyer to deduct and credit IVA |
| Signature | None | Signed with your CSD digital certificate |
| Cancellation | Informal | Governed by SAT's cancellation rules and approvals |
This is why a generic tool plays a supporting role here. A free invoice generator like FreeBillGen produces a clean, itemized billing document that captures the line items, amounts and IVA you will need, which you can share with your client or use to prepare the data. The official CFDI stamping itself still has to go through a PAC or SAT, because only they can apply the fiscal seal and folio.
How do you issue a compliant invoice in Mexico?
The issuance route can use SAT's service or compatible software and an authorized certification provider. Register with SAT and obtain the credentials and digital seal certificate required for your route. Collect the prescribed recipient data, classify the concepts, select the tax and Uso del CFDI codes, and submit the XML for certification. Deliver the certified CFDI in the required electronic form; a PDF is an optional readable representation.
Fiscal records generally have a five-year preservation period under the Federal Tax Code, but longer or different periods can apply. Preserve the certified XML and related records for the period that applies to the taxpayer and transaction.
- Register and get your certificates
- Obtain your e.firma and CSD from SAT so you can sign invoices in your own name.
- Capture the buyer's exact tax data
- Name, RFC, postal code and tax regime must match SAT's records under version 4.0.
- Build the invoice content
- Line items, amounts, IVA and any withholdings, plus the correct Uso del CFDI code.
- Stamp through a PAC
- Send the signed XML for validation; the PAC returns the CFDI and its SAT folio (UUID).
- Deliver and retain
- Provide the certified CFDI as required and preserve the XML and supporting records for the applicable period.
Mexico invoicing questions
What is a CFDI in Mexico?
A CFDI (Comprobante Fiscal Digital por Internet) is Mexico's mandatory electronic invoice. It is an XML document, currently in version 4.0, that is signed with your digital seal certificate, stamped by an authorized PAC and validated by SAT, the tax authority. Only a stamped CFDI with its SAT folio (UUID) is a valid fiscal invoice in Mexico.
Is a PDF invoice valid in Mexico?
Not on its own. A PDF is only a readable representation of an invoice. For tax purposes the valid document is the stamped CFDI 4.0 XML, validated by SAT through a PAC. A buyer cannot deduct an expense or credit IVA from a plain PDF; they need the CFDI with its unique SAT folio.
What is an RFC?
The RFC (Registro Federal de Contribuyentes) is Mexico's federal taxpayer registration code. CFDI 4.0 normally requires the recipient's RFC, registered name, fiscal postal code and tax regime. Generic RFC rules apply in specified cases, including some transactions with the general public or foreign recipients.
What is the Uso del CFDI?
Uso del CFDI is a SAT catalog code for the recipient's stated fiscal use, such as G03 for general expenses. It must be compatible with the recipient's registered tax regime. Ask the recipient for the correct current code.
Do I need a PAC to issue an invoice?
For most businesses, yes. A PAC (Proveedor Autorizado de Certificacion) is a SAT-authorized provider that stamps your CFDI and returns the official folio (UUID). SAT also offers a free issuing tool through its Factura Electronica portal for low-volume issuers, but in both cases the stamping and SAT validation are what make the invoice valid.
How long must I keep CFDIs in Mexico?
The general Federal Tax Code period is five years, but the start date and exceptions matter and some records must be kept longer. Preserve the certified XML and supporting records for the period that applies. A PDF is a readable representation, not a substitute for the XML.