As discussed in the past, we highly recommend your organization look at packaged solutions to solve compliance for Mexico CFDI. However, if you are looking to understand the process flow for an outbound Invoice in Mexico and the complexities -- below is what you will have to build. Remember, sending/receiving from the government is just part of the whole process. The most overlooked effort in any Mexico e-Invoicing project is the ERP configuration work.  Below is a sample of the inbound processes in Mexico for CFDI creation for an ERP system:

• Process begins with the Customer creating an ERP invoice via its standard ERPprocess, (like the SAP VF01 transaction). This triggers the creation of a billing document as per normal ERP processing during which your end solution should create a file format and transmit to your middleware solution. This is traditionally done via your standard ERP direct integration protocols. Note – the ERP configuration to create this message and manage the process internally is the most over looked portion of any project. Don’t under estimate this work load and the constant changes to these configurations that will be necessary over the years as legislation changes.
• Your CFDI compliance solution should receive the outbound file format, extract and package the data into SAT compliant XML and forwards it onto for fiscal validation, signature and approval. 
•  Your Compliance Server will log the inbound message, validate it for compliance to mandatory attributes and sign it using your government assigned digital seal certificate.  The message is transmitted in real time to the SAT servers, which then validates and approves as two asynchronous messages.
• Your solution should poll in real-time to obtain the approved SAT messages (including the SAT assigned timbre string), logging them into a long term archive repository, and then routing them back into your technical landscape for printing and updating in your ERP.
• Status messages should be conveyed back to the ERP for monitoring at all times.  Your end users need this to monitor the flow as well as have audit ready data in case of government requests. Aside from status messages, you should also build into the ERP system the ability to view/print the invoice, along with functions such as contingency mode, invoice cancellation, receiving and reject/retry.  These must be configured in the back-end system.
• After approval comes back from the government, the file format plus the SAT assigned protocol number is converted into a human readable invoice format and printed as additional shipment documentation accompanying the delivery.  Printing and the complexity with ‘extended attributes’ is often overlooked.  
• Also, the Invoice output format is expected to remain consistent across all ERP billing types and output conditions. 
• The SAT, typically when requested by the customer, requires the electronic facture be transmitted to the receiver in parallel to the delivery of the goods. This is typically accomplished via email in Latin America, so you will need to build this into your process flow. This way, when the truck arrives, the recipient will already have an electronic copy of the invoice to compare the printed output to whenever the goods physically arrive.
• The printed invoice may accompany the truck throughout for potential review by police or customs officials at any point along its journey.  The official can scan the bar-code printed on the PDF and can validate it in real-time with the SAT servers to establish the validity of the goods movement.  Finally, as the goods arrive at their ultimate destination, the receiver can validate the printed invoice through this same channel.