In German accounting, there is the rule, that a delivery (with few exceptions) has the same tax rate as the product delivered.

Product    Tax rate    Price

Book         7%            10€

DVD         19%           20€

In this case, that means, that the tax base for the delivery is

10/(10+20)   x  0,07   +   20/(10+20)  x  0,19 = 0,15 which is 15%

Does a solution exist? Maybe a workaround?

Thank you!