Sweden does not regulate prices on taxi rides, they may vary greatly. It is the customer's responsibility to check prices beforehand. You should check the price on the yellow label, which is usually on the rear door window, before entering the vehicle.
The price on the yellow label is based on a 10 km, 15 minutes journey and should be SEK 290 - 390. If the taxi you are about to choose has a higher price, look around for another car. When taking a taxi at a taxi station you do not need to take the first vehicle in line - you are free to select any taxi company. The price indicated on the taximeter is in Swedish kronor. Always ask for a taximeter receipt when paying for the journey.
At our hotel we always use the taxi company Taxi Stockholm which is a company we trust. There are many taxi companies with similar names so be careful when going into the car.