Getting started with the Marmin OMN E-Invoicing API

Welcome to the Marmin OMN E-Invoicing API. This overview walks you from creating your account to making your first API call, so you understand the full end-to-end flow.

If this is your first time integrating with Marmin, start here and then follow the links to the detailed Authentication, Business Profiles, Webhooks, and document APIs.

Understand the typical API workflow

Most integrations follow a common sequence: authenticate, set up your business configuration, then create and retrieve documents.

Authentication

• All Marmin APIs use JWT access tokens.

• Every API request must include a valid access token in the Authorization header.

• See the Authentication guide for the exact token endpoints and request/response formats.

Business setup

• Before you create any invoices or credit notes, configure your business profile in Marmin.

• See the Business Profiles documentation for the required fields and setup steps.

Note on customers and suppliers

• As an API integrator, you do not need to create customer or supplier master data in the Marmin UI.

• When you create invoices or credit notes via the API, you pass the full customer or supplier party details directly in the request payload.

Document generation

After authentication and business setup, you can start creating documents via the API. Marmin supports:

• Sales Invoices (type code 380) – standard invoices issued to customers.

• Sales Credit Notes (type code 381) – credit notes issued to customers.

• Sales Debit Notes (type code 383) – debit notes issued to customers.

• Purchase Invoices (type code 389) – self-billed invoices for purchases.

• Purchase Credit Notes (type code 261) – self-billed credit notes for purchases.

See the Sales Invoices and Purchase Invoices documentation for field-level details, validation rules, and full request/response examples.

Document retrieval

Once documents are created, you can retrieve them and their statuses through the API:

• Retrieve documents in JSON format for programmatic processing.

• Download documents as PDF files for human-readable viewing or sharing.

• Download documents as UBL 2.1 XML files for compliance and integration with other systems.

• Get document status and transmission logs for auditing and troubleshooting.

Use the navigation on the left to move from this overview into the specific topics you need: Authentication, Business setup, and the individual document APIs.