Start with the receiving system's requirements
Identify the recipient, required format, identifiers and route for exchanging the document. Check which fields are mandatory and how tax, currency, allowances and references should be represented. Establish which system owns the invoice number and final financial record. A sample exchange should test valid documents as well as missing information, rejected items and correction scenarios before the process is used for live billing.
Keep acceptance and correction visible
A technical transmission does not necessarily mean that the recipient accepted the invoice. Decide how receipt, validation and rejection information returns to your team, and who resolves an exception. Retain enough context to connect the exchanged data with the customer-facing document. Country rules and network requirements can differ, so a general e-invoicing capability should not be presented as automatic certification or support for every jurisdiction. Confirm the exact scope in your proposal.