Generate electronic invoices via REST API in a custom integration

The scenario

A software house or an in-house team running a proprietary ERP or checkout wants to generate electronic invoices directly from its own backend, without adopting n8n or a webhook-based flow: full control over how request, response, and retries are handled, inside its own codebase.

How it fits together

The POP API exposes a shared data payload across every format: the same structure generates FatturaPA XML (POST /create-xml, see api/sdi) or PEPPOL UBL (POST /create-ubl, see api/peppol) by calling a different route. Authentication is a single X-API-Key header carrying the account’s license_key.

The recommended path: get the key, verify it with GET /account-profile, generate a real document against the sandbox environment (no credits consumed, invoice_number prefixed SANDBOX-) to validate the integration, and only then add any delivery integration (native SdI/PEPPOL, webhook) to the production request.

Why it works

A team with its own engineering capacity avoids depending on an external automation tool and integrates fiscal document generation into the same codebase that already handles orders or internal billing. The sandbox environment lets it validate the integration end-to-end before touching real credits or data.