Mexico CFDI 4.0 for Freelancers: RFC, PAC, and ISR Retention Explained
How Mexican freelancers issue CFDI 4.0 compliant invoices, choose a PAC, and handle 10% ISR retention for professional services.
CFDI 4.0 is mandatory in Mexico since 2022
Since January 2022, every invoice issued in Mexico must be a CFDI 4.0 (Comprobante Fiscal Digital por Internet) — a structured XML file stamped by a PAC (Proveedor Autorizado de Certificación) authorised by Mexico's tax authority SAT. A PDF alone is not a valid fiscal document.
If you freelance in Mexico — whether as a designer, developer, consultant, or service provider — you need both an RFC (Registro Federal de Contribuyentes, 13 characters) and access to a PAC to issue invoices. Common PAC options for individuals and small businesses include Facturama, Edicom, and Solución Factible.
Open the freelancer generatorRFC: your tax identity number
Your RFC is your Mexican tax identity. For individuals, it's 13 characters (usually 4 letters from your name + 6 digits from your birthdate + 3 homoclave characters). For companies, it's 12 characters. You must include your RFC on every CFDI 4.0 you issue.
If you invoice a Mexican company (persona moral), you also need their RFC on the invoice. Without the recipient's RFC, the SAT may treat the transaction as if no invoice was issued and reject your client's input tax deduction.
ISR retention for professional services
When a Mexican company pays a freelancer (persona física con actividad empresarial) for professional services, the company must withhold 10% ISR (Impuesto Sobre la Renta) and pay it directly to the SAT. This is automatic and not optional — the company deducts it before paying you.
On your CFDI 4.0, the 'Total' amount is what you actually receive. The invoice typically shows: subtotal, IVA 16%, ISR retenido 10%, and the net total. This differs from how a company-to-company invoice looks (no ISR retention), so the invoice generator lets you set ISR retention per line.
Why a PDF invoice generator still helps
The PDF you generate with this tool is for client reference and your own records — the legally valid CFDI 4.0 must come from a PAC. However, structuring your line items in the generator first (description, quantity, price, IVA, ISR if applicable) makes the CFDI 4.0 generation through a PAC much faster and less error-prone.
Most freelancers draft the invoice in a generator, then transfer the same data to a PAC portal to generate the stamped XML. The PAC issues the official CFDI 4.0 with the UUID (folio fiscal) that the client needs for their accounting.