Short for standardized portfolio analysis of risk (SPAN). This is a leading margin system, which has been adopted by most options and futures exchanges around the world. SPAN is based on a sophisticated set of algorithms that determine margin according to a global (total portfolio) assessment of the one-day risk for a trader's account.
Options and futures writers are required to have a sufficient amount of margin in their accounts to cover potential losses. The SPAN system, through its algorithms, sets the margin of each position to its calculated worst possible one-day move. The system, after calculating the margin of each position, can shift any excess margin on existing positions to new positions or existing positions that are short of margin.