Implementing two distinct invoice sequences in Odoo, one following the native structure and another sourced from an external system, requires a combination of Odoo's configuration capabilities and potential customization. Here's how you can achieve this:​

1. Native Odoo Invoice Sequence:

• Default Sequence Configuration:
  • Odoo automatically assigns a unique reference number to each invoice using a sequence format like INV/year/incrementing-number (e.g., INV/2025/00001). 
• Customization of Sequence Format:
  • To modify the default sequence, navigate to the Accounting module, access the Customer Invoices journal, and adjust the sequence settings as needed.​

2. External Software Sequence Integration:

• Custom Field Addition:
  • Introduce a custom field in the invoice model to store the external sequence number. This can be achieved by activating developer mode and adding a new field to the customer invoice form.​
• Automation of Sequence Retrieval:
  • Develop a scheduled action or automated script within Odoo that connects to the external system's API to fetch the next available sequence number. This script should populate the custom field with the retrieved sequence.​
• Validation and Error Handling:
  • Implement error-checking mechanisms to handle scenarios where the external system is unreachable or returns an invalid sequence number. Ensure that the invoice creation process can gracefully handle such exceptions.​

3. User Permissions and Workflow Adjustments:

• Access Rights Management:
  • Ensure that only authorized personnel can modify the external sequence field to maintain data integrity.​
• Workflow Integration:
  • Incorporate the external sequence number into your invoicing workflow, ensuring that it appears on printed invoices and is included in relevant reports.​

At Wan Buffer Services, we've assisted clients in integrating external systems with Odoo to enhance operational efficiency. Implementing dual invoice sequences can streamline processes and ensure compliance with external requirements.