GRP Rainer Lawyers Tax Advisors, Cologne, Berlin, Bonn, Düsseldorf, Frankfurt, Hamburg, Munich, Stuttgart, Hanover, Bremen, Nuremberg, Essen and London www.grprainer.com/en explain: If a brokerage agreement concluded between a broker and an interested party is invalid, the broker may nonetheless be entitled to claim commission. This would firstly be conditional upon the broker acting as a salesman for the interested party, who must also be able to discern this. Additionally, the broker’s services have to be justified by the existing relationship between the parties concerned, i.e. the broker may not act without a legal basis from the perspective of the interested parties.