The Dutch Advertising Code Authority has published several examples on its website that can be used to make clear that there is a relevant relationship between the influencer and advertiser.
For example in relation to video (YouTube, Facebook, Instagram TV), several example phrases are provided that can be included orally or via text in the video and/or in the description under the video. When technically possible the text should be visible on all devices without having to click a "see more" button.
In relation to photos (Instagram, Facebook, Twitter), several examples of hashtags are provided that can be used in or under the picture or message.
In the case of a chain of temporary messages (Snapchat, Instagram Stories), the hashtag should in any case be included in the first and last published post and remain visible as long as the content is available.