Facturar en LÃnea (FEL) provides Mexican companies with electronic billing services. These services adhere to Mexico's legal requirements regarding the use of CFDIs in online billing. CFDI stands for Comprobantes Fiscales Digitales por Internet (trans. Digital Online Tax Receipts). The Remote Connection API provides programmatic access to FEL's billing services via SOAP calls issued in XML format. The FEL website is provided solely in Spanish.