Yes, agreed, a costly lesson for the next time. I am not naive about these matters but just expected a somewhat better (i.e. more regulated) taxi arrangement in The Hague. Nonetheless, hopefully this post helps other travelers to avoid a similar situation.

Did they use the meter to come up with a price of 23,50?

The driver had a meter down the side of the car but not very visible. He produced a hand-written receipt (- the taxi taking me back to the station had a proper print out). Unfortunately I accepted the charge without argument as I assumed (being in The Hague) that it was an honest price. It was only on mentioning to the hotel reception what I thought to be a high price for a taxi ride that they told me that I had been ripped off. Like I said, a lesson learnt the hard way, and hopefully this post helps others avoid the same trap.

Did the car have blue "plates"? Only taxis have blue plates. I too would expect Holland to be more honest. But we can meet all sorts in our travels.

Not that I noticed. I had meant to take a photo of the car with my phone but in the end the need to get out of the wind and rain impeded this. The car was in the official taxi rank so I assumed he had the approval of the other (legitimate?) drivers.

An unofficial taxi wouldn't last 1 minute in a taxi rank in NL. The problem in The Hague and presumably elsewhere in NL is that the taxi license is often unofficially sub-contracted out to family members and friends of the person it was awarded to. Quite a few times the driver has had to apologise to me for not knowing the way as the cab isn't his and he doesn't know how to operate the satnav ! The taxi companies are honest, the licensed drivers are more likely to honest than dishonest, but the "stand-in" drivers leave a lot to be desired.

Do you know whether the meters are required in The Hague? If so, where can you report this type of cars?

I'm arriving in The Hague next month. Is there a way I can avoid the rogue taxi drivers in the queue? I will certainly ask for a price/estimate up front and make sure they have a visible meter, any other tips? This has been helpful, thank you.

The following link is a complete list of approved Taxi Companies operating in The Hague.

http://www.taxibelle.nl/taxibedrijven/zuid-holland/den-haag/

A Gemeente recommended agency for pre-booking taxis, if you would like that - is

http://regiotaxi.haaglanden.nl/contact

The following link is a place to report any problems with a Taxi Driver. So you can ask for fare by the meter and also note the number of the taxi so that in case there is an issue / dispute. Taxis should have a visible meter normally and if you can not see it, then ask the driver where is the meter.

http://www.taxiklacht.nl/pages/taxiklacht/KLACHTEN?windowuid=uid1408613805