This article is aimed at anyone who has updated Frisbii beyond version 5.4 (Winter'25).
You can apply these actions to the sandbox for testing, and then to your organization when you go live.
Please note the actions to be taken following the Frisbii update.

Invoice issuing country based in France
All your corporate names in Frisbii have an Invoicing country in France, then you are concerned by the following:

After updating to Frisbii 5.4 or higher, as an Administrator you only need to take a single action on your sandbox and when switching to production: fill in the reference billing country used by each Frisbii user (Finance, Sales and Administrator.)
From Salesforce Configuration, on the relevant user, fill in the new "Invoicing country" field with the appropriate invoicing country.
This value is required to add an Invoice Line item / Subscription Line Item /Quotation Line Item / Opportunity Product, as well as to create or modify Product / Accounting Data / Product Rule and Corporate Name records.
Please refer to the following article for more details on use cases.
Invoice issuing country based in Europe (excluding France)
At least one of your corporate names in Frisbii has an Invoicing country different from France, then you are concerned by the following:

After upgrading to Frisbii 5.4 or higher, as an Administrator, you must perform the following actions on your sandbox and when switching to production:
Enter the reference billing country used by each Frisbii user (Finance, Sales and Administrator.)
From Salesforce Configuration, on the user concerned, you must fill in the new "Invoicing country" field with the appropriate invoicing country.
This value is required to add an Invoice Line item / Subscription Line Item /Quotation Line Item / Opportunity Product, as well as to create or modify Product / Accounting Data / Product Rule and Corporate Name records.
Please refer to the following articlee for more details on use cases.
You already created new VAT values in the drop-down list sofactoapp__TVA_par_defaut2__c and sofactoapp__Taux_de_TVA_list__c before Frisbii update 5.4?
We recommend deleting these values, as the update automatically adds European VAT rates to countries. For each country, you'll find only the VAT rates concerning that country. VAT rate values are no longer mixed up, and drop-down lists are clear and easy to read.On the Account object, the new VAT management rules in Frisbii are not applied.
There are 2 ways to manage VAT on accounts:Either continue to use the VAT drop-down list with all the values you've already created.
Or you can make the necessary customizations to create the dependency between the Account's billing country and the Account's VAT drop-down list. Territory activation will be required for your organization.
Important if you do not use the VAT rate on the Account in your Billing process, you have no action to take.