Hi, I understand that in the U.S. the options margin requirements, which are rule based, should not be higher than the maximum possible loss of an option spread position. So that, for example, the margin of a short vertical put of 10 points should not be higher than USD 1000, under any circumstances. However, there are derivative exchanges, such as Eurex, that use SPAN margin system and not the rule based margin system as in the U.S. Theoretically, this should be a favorable margin treatment, since the SPAN is a more sophisticated margin system which try to accurately evaluate the true risk of the position, and should not require margin which is higher than the maximum possible loss. Nevertheless, I encountered a different reality: I have entered a few positions to my account, in which I was required to add margin in addition to the premium that I received, so the aggregate amount (premium amount + additional margin) was actually higher than the maximum possible loss. For example, for a short vertical put of 10 points, for which I received a premium of 950 (it was in the money), I was required to provide an additional margin of 100, so the aggregate margin requirement was 1050, which is higher than the maximum possible loss of 1000. Another example: shorting a 12 points iron condor would require margin of 1420, and not 1200. The reason (of my broker and Eurex): the SPAN algorithm calculates the risks of the legs of the positions and may require these additional sums. Can someone please explain me the logic of this method? It sounds to me an inferior method to the U.S. rule based margin requirements, in which the trader can know in advance what are the margin requirements and not be subject to some algorithms that "calculate" the "true" risk of the position and actually requires margin which is higher than the maximum possible loss. Thanks.