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FirmaSAT On-line Validator

Servicio de Administración Tributaria (SAT) Mexico
Comprobante Fiscal Digital por Internet (CFDI) versions 4.0 and 3.3
Timbre Fiscal Digital versions 1.0 and 1.1
Retenciones e información de pagos versions 1.0 and 2.0
Contabilidad electrónica versions 1.1 and 1.3
Controles volumétricos versions 1.1 and 1.2
FirmaSAT utility

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.

2025-08-01: Sorry! The On-line Validator page has been down. We apologise if you came here and it didn't work. It's back working now. It seems our web hosting service (who up until now have been great) started a new virus checker that literally just deleted our pages even though they are valid. B*stards! Thanks to Kevin Powick for telling us.

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 supplements (complementos).

Changed in February 2025: For the latest specifications of the complementos see

https://www.sat.gob.mx/portal/public/tramites/complementos-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

cfdi:Comprobante v4.0 with optional tfd:TimbreFiscalDigital^† v1.1
cfdi:Comprobante v3.3 with optional tfd:TimbreFiscalDigital^† v1.1
cfdi:Comprobante (legacy) v3.2 with optional tfd:TimbreFiscalDigital^† v1.0
retenciones:Retenciones v2.0 with optional tfd:TimbreFiscalDigital^† v1.1
retenciones:Retenciones with optional tfd:TimbreFiscalDigital^†
catalogocuentas:Catalogo
BCE:Balanza
PLZ:Polizas
RepAux:RepAuxFol
AuxiliarCtas:AuxiliarCtas
sellodigital:SelloDigitalContElec^†
controlesvolumetricos:ControlesVolumetricos versions 1.1 and 1.2

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.

Disclaimer

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 17 August 2025

Contact us

To contact us, please send us a message.