Hi everyone,

I’m dealing with a strange issue that started right after upgrading one of my databases from Odoo 17 Enterprise to Odoo 18 Enterprise. The problem appears on invoices that come from Subscriptions. (I dont have a normal sales on this project, they sell only services with subscription)

What’s happening

When I try to create a credit note using the standard “Add Credit Note” button on a posted customer invoice, Odoo throws this error instead of generating the credit note:

The unit of measure Units defined on the order line doesn't belong to the same category as
the unit of measure False defined on the product. Please correct the UoM on the order line
or on the product. They should belong to the same category.

The key part is that Odoo says the product’s UoM is False, even though in the product form the UoM is definitely set and it was working fine before the upgrade.

What I already checked

• The product UoM is correctly set (in the UI and in DB).

• The sale order line UoM is set.

• Invoice line UoM appears normal.

• All UoMs belong to the same category.

• No custom modules involved.

• I verified the DB entries directly (product_template, sale_order_line, account_move_line).

If anyone has run into this before, or knows how to properly fix UoM data for subscription invoices in Odoo 18, I’d really appreciate any guidance. Thanks in advance!