In standard OpenERP, you can choose a fiscal position for every partner, and your choice will be used when you select a Partner in an Invoice or Sale Order. In many situations it’s convenient to set a default position for all partners belonging to a specific country.
The module we developed is called account_fiscal_position_country, and can be found on apps.openerp.com.
Configuration
Go to Sales > Configuration > Address Book > Localisation > Countries.
Choose a country, and enter the default Fiscal Position for that country.
Usage
Done that, when you create a Sale or Purchase Invoice and select a Partner, the Fiscal Position you defined for the country of the Partner will be selected. Note that the standard OpenERP behaviour is still defined: if you set a specific Fiscal Position for that Partner, that one (and not the one from the Country) will be used.
Sale Orders
To get the same functionality in Sale Orders, install the module account_fiscal_position_country_sale as well. The modules are kept separate to minimize dependencies.
Of course, feedback is welcome! You can use the bug tracker in launchpad for that: