The health insurance companies submit the premiums they propose to charge for the following calendar year, by canton, to the Federal Office of Public Health (BAG) at the end of each July. These are based on the expected costs per canton. The BAG is mandated by the Federal Council to check whether the proposed premiums are appropriate in relation to the costs the insurers are required to bear in the respective canton. Given the large number of unknown factors (such as how costs will develop in future), a degree of uncertainty is always involved in calculating premiums. That is why insurers establish provisions and reserves. As health insurers are not allowed to make a profit out of basic insurance, the money therefore remains in the system and is used solely to pay benefits, and for no other purpose. However, reserves are not calculated on a cantonal basis. This gave rise to the minimal differences between premiums revenues and the costs of healthcare per canton. The cantons have now asked for these differences to be redressed. Politicians have approved this request. In other words, premiums have always been calculated correctly. However, a political decision has been made to change the rules retroactively.