How to Integrate a Payment Gateway with a Custom Module in Odoo 18?

[Vihan Richard]

Integrating a custom payment gateway into Odoo 18, especially when working with a tailored module outside of standard eCommerce or Invoicing apps, requires a good understanding of Odoo's payment acquirer model. Unlike older versions, Odoo 18 emphasizes modular integration via payment acquirer and payment transaction models.

If you're building or modifying Odoo payment apps, it’s better to extend existing payment models rather than creating from scratch—this allows smoother backend configuration and compatibility with payment workflows.
For developers working with custom flows, here are a few helpful tips:

Use the payment register wizard for transaction processing.
Ensure the external API communication is handled with proper error catching and logging.
Make sure your Odoo payment methods follow the expected state transitions (draft → pending → done/failed).

Anyone else working with Odoo payment gateway integrations in 18?
Would love to hear how you've structured your flows or dealt with challenges like tokenization or partial payments.