Margin requirements on Debit call Spreads

[spindr0]

Quote from Trader7793:

When I worked at Ameritrade years ago they had a margin requirement on doing debit spreads...of the difference between the strike prices x the number of shares...this was even in their margin handbook. I had always assumed that every firm used that formula.

It seems that some firms do not place that margin requirement on debit spreads?

Margin for debit verticals is the premium paid. For credit verticals it's the difference in strikes less premium received. IOW, it's the max loss of the spread.

However, brokers have the right to impose higher margin requirements which it appears Ameritrade was/is doing (difference in strikes).

For margin calc's, see:

http://www.cboe.com/tradtool/mCalc/default.aspx