Do I need to register at KVK to do small paid jobs on the side?

In NL you must register at KVK if you structurally offer services for payment, regardless of income. There is no "threshold" like in some countries. Exception: truly occasional (1-2x per year, under 500 EUR total, no advertising) MAY qualify as incidenteel werk. Doing weekends regularly = kvk-plichtig. Registration costs 80 EUR one-time. Not registering risks 20-400 EUR fines plus full tax investigation. Its cheaper to just register as ZZP.