I have a question reguarding bull call spreads. I am going to use a current example of a stock I picked out. Lets use CitiGroup. Right now Citi is trading at $3.53 and lets say I think its going to go up. So I look up the Call list and find the March calls with 74 days to expiration. I buy 10 March 3 calls for $620.00 Write 10 March 4 calls for $140.00 This leave me with a Net debit of $480.00 Now my question is this. Lets say Citigroup goes up to $6.00 and before expiration my calls that I wrote get exercised (Or even at expiration). Do I have to have the capital in my account to transfer all the stock? Meaning 1000 shares of citigroup at $4.00 equaling $4,000? Or is it done instanteously without requiring the full capital because of the previous calls that I own?