The European Commission has opened an investigation into the Danish taxation regime of online casinos. The focus of the investigation is that Denmark charges a flat rate tax of 20 per cent on the gross gaming revenues of online casinos compared with 75 per cent for land-based casinos and gaming halls. It is not clear whether the difference in rate can be objectively justified. The Commission has received two complaints alleging that the planned measures violate EU state aid rules. The investigation takes place in the context of Denmark’s recent move to liberalise its gambling markets by granting licences to online gambling providers. The partial liberalisation is due to take effect on 1 January 2011 but is subject to prior approval from the Commission.