A Foreign Term for an Addendum
'Rider' is a term, primarily used in US law, that is synonymous with an addendum or appendix. It refers to a separate document that is attached to a main contract to add, amend, or clarify specific terms. In the Dutch rental context, you are more likely to see the term addendum or bijlage (appendix). A rider could be a standard set of clauses that a large property management company attaches to all their leases, such as their specific house rules, privacy policy, or regulations for making alterations to the property. Once attached and signed, a rider legally becomes part of the main rental agreement.
Subject to Mandatory Dutch Law
The most important thing for a tenant to understand is that no matter what a document is called—a rider, an addendum, or a side letter—its content is always subject to the mandatory provisions of Dutch tenant protection law (dwingend recht). A landlord cannot use a rider to make a tenant sign away their fundamental rights. Any clause in a rider that conflicts with these mandatory laws is automatically void (nietig) and has no legal effect, even if the tenant has signed it. For example, a rider that requires a tenant to give three months' notice to terminate the lease is void, because the law mandatorily sets the tenant's notice period at one month. A rider can supplement the lease, but it cannot weaken the tenant's core legal protections.