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FirmaSAT On-line Validator

This is the FirmaSAT (unofficial) validation page. The FirmaSAT On-line Validator checks Comprobante documents (CFD and CFDi) and Retenciones and Contabilidad and Controles Volumetricos documents against the published specifications of the Servicio de Administración Tributaria (SAT). This validation service is provided for information only.

Click here to use the FirmaSAT On-line Validator.
This is intended to work in a similar manner to the (old, now defunct) official SAT validator pages. Our validator handles all versions (including CFDi v4.0 and v3.3) on one page and includes support for all the latest SAT invoice complements which are currently listed in a PDF document MenuComplementos.pdf (archived copy) This PDF file is "hidden" in a link at the bottom right of the SAT page Consulta los complementos y complementos concepto de factura.

2023-10-01: Added support for Complemento Carta Porte 3.0.

2021-12-22: Added support for CFDi v4.0.

2014-07-03: See The logic behind the FirmaSAT On-line Validator which explains the logic behind the FirmaSAT On-line Validator and shows the function calls from the FirmaSAT library.

Supported document types

The following types of XML documents are supported

All the documents above will have their signature verified using the embedded `certificado` field, except those marked which require the user to upload the `Certificado del SAT` file as well.

Show the QR Code (CFDI v4.0/v3.3 only)

The validator will produce a QR Code image as specified by SAT (pdf) and ISO/IEC 18004:2000. Only v4.0/v3.3 CFDI documents with an TimbreFiscalDigital element included will produce a QR code.

You can select the size from 2 pixels per module (about 3cm × 3cm) up to 16 (22cm × 22cm). A module is the small black or white square in the image.

Use our diQRcode product to generate QR code images directly from your code or the command line. See QR code for CFDi.

The software

The FirmaSAT software behind our validator page is available here. You can call all the necessary functions to do the validation from your own VB/VBA/C#/C/C++/Python programs or use the command-line utility. The logic and function calls used are explained in The logic behind the FirmaSAT On-line Validator.


We provide our FirmaSAT software as an independent third party to users in Mexico and elsewhere who wish to create and check digitally-signed CFD and CFDi documents according to the published specifications of the Servicio de Administración Tributaria (SAT). We have no connection whatsoever with or any endorsement from the Servicio de Administración Tributaria in Mexico. We are not a Proveedor Autorizado de Certificación (PAC). We just provide software that works.

This service checks that the XML structure of the uploaded file is valid (with some minor exceptions) and that the Comprobante and Timbre Fiscal Digital signatures can be verified using the X.509 certificates provided. It does not check the validity of dates or any additional business rules. Other validation sites may carry out other checks that we do not do, like checking dates and RFC numbers. Please make your own judgments on the results provided. No warranties. Use at your own risk. This service is provided for information only. The results have no legal status.

This page last updated 2 October 2023

Contact us

To contact us, please send us a message.