RFC Validation API
Validate the RFC in real time against the SAT registry: confirm it exists, is active and can receive invoices, before you issue your CFDI. Individuals and businesses.
An API key is required to use this API. Official SAT source.
Sign Up to Get StartedDid you know Mexico's SAT no longer allows requiring the tax status certificate to invoice? Stop asking for the CSF and validate the RFC in real time. Read why →
Features
✓ Individual & Business RFC
Complete validation for individual RFC (13 characters) and business RFC (12 characters).
✓ Real-Time Validation Against the SAT
A live query to the SAT's RFC Validation service. Not a local computation: it confirms whether the RFC exists and is active in the registry.
✓ Invoice-Ready Check (accept_cfdi)
The response tells you whether the RFC can receive invoices, so you catch the RFCs that cannot receive a CFDI before stamping.
✓ The SAT's Own Message in Every Response
The reason field returns the SAT's own message, ready to show to the user or log in your system.
API Endpoint
GET https://api.tlaloc.sh/mx/v1/rfc?rfc={rfc}
Parameters
| Parameter | Type | Required | Description |
|---|---|---|---|
rfc |
string | Yes | RFC to validate (12 or 13 characters) |
Example Request
You need a Bearer API key (prefix tlmx_) generated in the console.
curl -X GET "https://api.tlaloc.sh/mx/v1/rfc?rfc=JUPC850621AB5" \
-H "Authorization: Bearer tlmx_YOUR_API_KEY"
The example RFC is fictitious — we don't publish real personal data. Replace it with a real one to get a valid response.
Example Response
{
"valid": true,
"accept_cfdi": true,
"reason": "RFC válido, y susceptible de recibir facturas"
}
Use Cases
Electronic Invoicing
Validate customer RFC before issuing electronic invoices.
Tax Compliance
Verify that suppliers and partners have valid RFC.
E-commerce
Validate RFC during checkout for automatic invoicing.
Payroll Management
Verify employee RFC for correct tax calculations.
Frequently Asked Questions
What does the API return when validating an RFC?
Three fields: valid (whether the RFC exists in the SAT registry), accept_cfdi (whether it can receive invoices) and reason (details when something doesn't match). The lookup runs in real time against the SAT registry, not against downloaded lists.
Can it also validate the name and postal code?
Yes. The optional nombre_razon_social and codigo_postal parameters verify an exact match against the registry — the same three checks SAT applies when stamping a CFDI 4.0 invoice, so you catch the mismatch before issuing instead of after the rejection.
Do I need to ask my customers for their Tax Status Certificate (CSF)?
No — and since November 2025 requiring it to issue an invoice is an infraction subject to fines in Mexico. Validating the RFC, name and postal code in real time is enough. Read Stop Asking for the Tax Status Certificate.
Does it work for individuals and companies?
Yes: 13-character RFCs (individuals) and 12-character RFCs (companies).
How much does each validation cost?
$0.10 MXN (0.10 units) per lookup, VAT included, prepaid with no monthly fees.
What is this API typically used for?
Validating invoice recipients before stamping CFDI 4.0, onboarding suppliers and customers with correct tax data, and cleaning catalogs of invalid or inactive RFCs.