This does not work for me, either.  When I went to create a credit note from a customer invoice, Odoo assigned an INV number that had already been used.  Why would it do that?

I also see a comment (the first one?) which states to simply reverse & it creates an editable credit note. However that does NOT happen. My credit note was NOT editable. So I had to create a new invoice to be the non-refunded amount, which is very sloppy, PARTICULARLY because it’s a deposit invoice, which should be an actual sale. 

Just click REVERSE.

This gives you an editable Credit Note for 100% of the value of the Invoice.

You then edit the account and reduce the amount down to the value you wish to credit back the Customer (keep the amount positive).

If the "Partial Refund" option is not appearing in Credit Notes in Odoo 17, it is likely due to misconfiguration or a missing setting. Here's how you can enable and use the "Partial Refund" option:

1. Check Credit Note Settings

Ensure that the Credit Note functionality is fully enabled and configured in your Accounting module.

1. Enable Credit Notes:
   • Navigate to Accounting > Configuration > Settings.
   • Ensure the Credit Notes option is enabled.
   • Save the settings.
2. Verify User Permissions:
   • Go to Settings > Users & Companies > Users.
   • Open the user account.
   • Under Access Rights, ensure the user has sufficient rights for Accounting:
     • Set to Adviser or Manager.

2. Verify the Credit Note Options

When creating a credit note, the options (Partial Refund, Full Refund, etc.) are tied to the state and configuration of the original invoice.

Steps to Generate a Credit Note with Partial Refund:

1. Navigate to Accounting > Customers > Invoices.
2. Open the invoice for which you want to issue a credit note.
3. Click the Credit Note button.
4. In the wizard that appears:
   • If the "Partial Refund" option is not visible:
     • Ensure the invoice is in a posted state (not draft or canceled).
     • Check if the invoice has been paid partially or fully (affects the refund options).

3. Partial Refund Configuration

If the "Partial Refund" option still does not appear, ensure the credit note logic is aligned with partial refunds:

1. Enable Restocking Fee Feature (Optional for Restocking Fees):
   • Navigate to Accounting > Configuration > Settings.
   • Enable Discounts and Fees under the Invoicing section.
   • Save the settings.
2. Manually Adjust the Credit Note for Partial Refund:
   • After clicking Credit Note:
     • Select Full Refund (if "Partial Refund" is not visible).
     • Edit the credit note form to reflect only the items or amounts being refunded.
     • Add a line for the Restocking Fee as a negative amount to reduce the refund total.
   • Example:
     • Refund Item: $100 (Refund Amount).
     • Restocking Fee: -$20.
     • Net Refund: $80.

4. Apply Customization for Partial Refund (if Necessary)

If your business process frequently involves partial refunds with restocking fees, you can customize the behavior:

1. Add a "Restocking Fee" Option:
   • Navigate to Accounting > Configuration > Journals > Customer Invoices.
   • Add a default Restocking Fee product or account to automate the calculation.
2. Create Automated Partial Refund Logic:
   • Use a custom module or Odoo Studio to modify the Credit Note wizard to include a "Partial Refund" template that automatically adjusts the refund amount and adds a restocking fee line.

5. Troubleshooting Tips

• Option Not Appearing:
  • Check the invoice state. The Credit Note options may not appear for invoices in Draft or Canceled states.
• Access Rights Issue:
  • Ensure the user has the necessary rights to manage invoices and refunds.
• Customizations or Bugs:
  • If your Odoo instance has customizations, the Credit Note options might be affected. Disable the customizations temporarily to verify.

6. Summary

To enable and use the "Partial Refund" option:

1. Ensure the Credit Notes feature is enabled in Accounting settings.
2. Verify the invoice state and user permissions.
3. Adjust the credit note manually for partial refunds and restocking fees if necessary.
4. Use Odoo Studio or a custom module for automation if partial refunds are frequent.

If these steps don't resolve the issue, let me know, and we can explore deeper technical solutions!