Hi everyone,
Maybe that you already met the case, but there is a new VAT rule for e-commerce which has been released in Europe since the 1st of July 2021.
For legal documentation, please find some information in this link : https://ec.europa.eu/taxation_customs/business/vat/vat-e-commerce_en
This new system is called One Stop Shop (OSS). In summary, the basis of this new rule is to apply the local VAT rate of european e-customer.

In order to stay compliant in Odoo, there is a new feature "EU Intra-community Distance Selling", available in the settings of the Accounting app (only available in v14), under the taxes' section. Please note that you will maybe need to update the accounting module at first.

This feature will automatically generate the fiscal positions for each country in Europe and the related taxes.
For example, in the fiscal position "OSS B2C France", you will find under the tax mapping the three belgian rates (for a Belgian company) that will be updated with the three french rates. So once Odoo will recognize a sale to a French customer (without a VAT number), it will apply the French rate instead of the Belgian rate.

I hope that it will help you.
Regards,
Jérôme