Taxi service was traditionally a tightly guarded monopoly. In recent years, the market was deregulated, but prices are still high. Taxi drivers are licensed, but they do not, as of yet, have to pass a proficiency exam, providing they know the streets. This is planned in the future, since the taxi market is being re-regulated. In the bigger cities taxi drivers can be unfriendly to very rude. One will find that especially in the western part of the country the cost of a taxi are very high for very little politeness and service. The public transport system often proves to be cheaper and a lot faster. If you have to rely on a taxi, there is a free smartphone app for ordering taxis in most of the major cities in the Netherlands that gets you a responsible driver, and helps you keep track of the route and price.
Some taxi drivers refuse short rides (e.g. under €10). This is illegal, but it’s hard to enforce this prohibition. There is a maximum tariff (about €3.00 curb call plus €2.10 per km traveled), and it’s built into the taxi meters. If you negotiate a price before you get in, the price you have to pay is the negotiated price, or the metered price, whichever is lower. Getting in a cab without enough money to pay for the ride is illegal, so it’s wise to negotiate a price. Note that most taxi’s only accept payment in cash, debit or credit cards cannot be used. Around Amsterdam and to some extent Utrecht, Uber taxi’s are available and can be paid for online.
All legal taxis have blue license plates. So do some other vehicles for group transport, such as minibus services for the handicapped.