A trustmark is not a quality judgement but a contract. The question is not how trustworthy the logo looks, but whether there is a dispute scheme behind it and who guarantees compliance.
A trustmark is worth something if it has three things: a public register in which you can find the retailer, a dispute scheme you can turn to, and a guarantee that the decision will be complied with if the retailer does not do so itself. If any one of those three is missing, the logo is just an image.
A trustmark logo on a website is a picture. It can be lifted from another site with a right-click. Every serious trustmark therefore maintains a public register of affiliated retailers. The only meaningful check is: look the retailer up in that register, on the trustmark's own site and not through a link on the retailer's site.
If the shop is not listed, it is displaying the logo without entitlement. That is in itself an unfair commercial practice within the meaning of article 6:193c of the Dutch Civil Code, and an independent argument in a file.
The best-known trustmarks for Dutch retailers are Thuiswinkel Waarborg, WebwinkelKeur and Keurmerk Webshop. They differ in admission requirements and in what they do afterwards. What you want to know for each:
The regulations are revised periodically and so are the amounts. Before relying on a guarantee, always check the current regulations on the trustmark's site.
To a retailer the trustmark is a marketing investment. It sits in the checkout because it raises conversion. A complaint file with the trustmark holder therefore touches something the retailer does feel, even where a claim of a hundred euros does not.
We therefore report to the trustmark holder as standard as soon as a deadline passes. In a proportion of files, payment follows within days of that report without anything further being needed. That is not a threat but the use of a scheme the retailer voluntarily bound itself to.
We report the file to the trustmark holder as soon as the deadline passes. That works more often than a reminder.