The provision of online advertising generally involves several actors, including intermediary services that connect publishers of advertisements with advertisers. Codes of conduct should support and complement the transparency obligations relating to advertising for providers of online platforms, of very large online platforms and of very large online search engines set out in this Regulation in order to provide for flexible and effective mechanisms to facilitate and enhance the compliance with those obligations, notably as concerns the modalities of the transmission of the relevant information. This should include facilitating the transmission of the information on the advertiser who pays for the advertisement when they differ from the natural or legal person on whose behalf the advertisement is presented on the online interface of an online platform. The codes of conduct should also include measures to ensure that meaningful information about the monetisation of data is appropriately shared throughout the value chain. The involvement of a wide range of stakeholders should ensure that those codes of conduct are widely supported, technically sound, effective and offer the highest levels of user-friendliness to ensure that the transparency obligations achieve their objectives. In order to ensure the effectiveness of codes of conduct, the Commission should include evaluation mechanisms in drawing up the codes of conduct. Where appropriate, the Commission may invite the Fundamental Rights Agency or the European Data Protection Supervisor to express their opinions on the respective code of conduct.