Why Does My Account Window Display A Margin Requirement When All Positions Are Long And Fully Paid?

We will calculate and display a margin requirement on the entire portfolio of positions held in an account even if the account holder has paid for the positions in full and is not borrowing any funds to support them. This is necessary in order to compute the Available Funds (Equity with Loan Value - Initial Margin Requirement) on hand to support any subsequent trade activity.