The Open Zaak project was initiated shortly before the 1.0 release of the VNG standards for "API's voor Zaakgericht werken", on August 1, 2019, by 9 municipalities:
- Amsterdam
- Rotterdam
- Utrecht
- Tilburg
- Arnhem
- Haarlem
- 's-Hertogenbosch
- Delft
- Hoorn, Medemblik, Stede Broec, Drechteland, Enkhuizen (SED)
Using Dimpact as a legal entity, they formed a project to develop a modern, open-source data- and services-layer to enable zaakgericht werken, in line with the Common Ground model.