The Dutch government decided that the freedom of movement of workers from Croatia is postponed until 1 July 2018. This means that employers intending to employ Croatian nationals will need a work permit until that date.
When Croatia joined the EU on 1 July 2013, the Dutch government decided that the freedom of movement was postponed until 1 July 2015. So this period is postponed with another 3 years. The Netherlands can postpone the freedom of movement of workers until 1 July 2020.
There is an exception to the work permit requirement for Croatians who have been working with a valid work permit for a year. In that case a work permit is no longer required.