KNWU
Ask for a KNWU membership number.
The Royal Dutch Cycling Union or KNWU (in Dutch: Koninklijke Nederlandsche Wielren Unie) is the national governing body of cycle racing in the Netherlands. More than 350 cycling associations in the Netherlands are affiliated with this federation. There are approximately 9,500 cyclists with a competition license member of the KNWU. If you organize a cycling event with Atleta you can ask for a KNWU membership ID to check whether the participant has a valid competition license. In addition you can give a discount to KNWU members or make a membership ID mandatory.
How does it work?
Configure an extra pricing rate for your tickets, and call it something like KNWU members.
Add a custom field for tickets, choose KNWU: license as field type and select the tickets and KNWU rates that apply.
Participants can now choose the KNWU rate and fill out their membership ID in the checkout.