du et des Prinzip

In Latin, do ut des means "I give, so that you give". This is a juristic equation so that both parties have equal benefits or obligations which promotes social cohesion. Other similar latin phrases would be "quid pro quo", or "this for that", and also "manus manum lavat" which means, "One hand washes the other".

This especially holds true in the case of Umsatzsteuer (but not for der Eigenverbrauch - nicht abzugsfähig.