Sales object tax id number

Why is the company taxi id number fetched to sales object basic data and where is it used?

1. I´ve tested to setup two different supply coutnries in Tax Liability Countries on Company/Tax control tab. One country is the same as the company country.
2. Setup of new sales object. Assume it fetches the company country tax id as default to the sales object. It is not editable.
3. Setup a customer address with the two supply countries defined on the company.
4. Create two instant invoices, one per supply country.

The invoice footer prints the tax id nunber from company setup depending on supply country.

Tax transaction window shows the invoices with the different tax id nunber.

I cannot see the sales object information is used for anything.