Trade v Position or Net v Gross generally positions in a proprietary or house account will be held net, whereas positions in an omnibus client account will be held gross. Net v Gross becomes important when looking at the Initial Margin calculation because of the difference between US and European regulation.
US regulation allows a 1 day Holding Period to be used, as long as this is calculated based on Gross positions for client accounts. European regulation requires a 2 day Holding Period using net positions. This has led to the EMIR add-on, used to scale up Initial Margin from a 1 day to 2 day Holding Period. A factor of √2 is used to increase the Initial Margin requirement – usually by increasing the parameters by this scalar and then recalculating.