The Spanish chart of account defines some accounts for sales and other accounts for sale returns. This means that for the same product a different account can be used depending if there is a sale or a sale return.
For example, when selling a product we will use the 700 account but when a customer returns the same product the account 708 should be used.
Currently it is not possible to define this configuration on tryton (we only allow a single revenue account per product) but I think it will be possible to implement using a custom module.
Is there any other countries that have similar needs? How did you solved?