An example of the existence of an agency agreement, which was the subject of legal proceedings dating back to 2006, came when a sponsor of a tennis tournament sued Venus and Serena Williams who had not participated. The sponsor claimed that his father, Richard Williams, had committed to participate in the tournament. The Williams sisters argued that their father did not have the authority to match them to such an agreement. If his father forced the sisters to play, the court had to decide whether there was a valid agency agreement between the Williams sisters and their father. If not, they were probably not bound by its agreement in accordance with Agency law. [must update] The definition of an agency agreement for the application of section 101 is based on the financial or commercial risk that the agent bears with respect to the activities for which he was designated as an agent by the adjudicator authority (see judgments in T-325/01 of September 15, 2005, Daimler Chrysler/Commission); Case C-217/05, 14 December 2006, Confederacion Espanola de Empresarios de Estaciones de Servicio/Cepsa and Case C-279/06, 11 September 2008, CEPSA Estaciones de Servicio SA v. LV Tobar e Hijos.SL. In this regard, it is not essential for the assessment to know whether the agent is acting for one or more large obligations. Nor does this assessment matter in terms of the assent of the parties or the national legislation. An important feature of agency contracts is also the right to a customer tax (in practice called „goodwill fees“) that the sales agent may have at the end of the agency contract.

In accordance with section 7:442 of Book 7 of the Dutch Civil Code, a sales agent is entitled to a customer tax at the end of the agency contract if the agency contract is terminated: the right to compensation of the client expires as soon as the sales agent has not informed the client that he is seeking such compensation within one year of the end of the agency contract. With the exception of the above case, the goodwill tax cannot be waived, since the provision is mandatory under section 7:442 of the Dutch Civil Code. The amount of customer charges depends on a number of circumstances. First of all, it is important that customer costs are never higher than one year`s pay. The above remuneration is calculated by calculating the average of earnings over the previous five years. If the agency contract lasted less than five years, the average of the last few years is taken. The fact that the remuneration is never higher than that of one year does not mean that the remuneration always corresponds to that average remuneration.