Schwab. $0.25 per contract, if I trade more than 1 contract, the commission per contract is less, on a sliding scale. Of course I trade a lot and don't know if they give me special rates because of that.
Lightfightercap If you have a resting order there are many participants who subscribe to the complex order books and will fill your order if it meets their edge requirements. Our backtester had slippage assumptions based on our fill experience as follows: Slippage is the extra amount paid or the smaller amount received for an option bought or sold compared to the middle of the options bid-ask. We use a percentage of the options bid-ask spread to represent this amount and the percent slippage is different depending on how many legs there are in the trade. The slippage formula to buy is: Bid + (Ask - Bid) * slippage% The slippage formula to sell is: Ask - (Ask - Bid) * slippage% The following table explains the default method to calculate slippage on entering and exiting a trade: # of Legs Slippage % bid x ask Buy Trade Price Sell Trade Price 1 .75 1.20 x 1.40 1.35 = 1.20 + (1.40-1.20) * .75 1.25 = 1.40 - (1.40-1.20) * .75 2 .66 5.10 x 5.90 5.628 = 5.10 + (5.90-5.10) * .66 5.372 = 5.90 - (5.90-5.10) * .66 3 .56 4.20 x 5.20 4.76 = 4.20 + (5.20-4.20) * .56 4.64 = 5.20 - (5.20-4.20) * .56 4 .53 8.50 x 10.30 9.454 = 8.50 + (10.30-8.50) * .53 9.346 = 10.30 - (10.30-8.50) * .53 According to the table above: for a 1 leg option trade like buying a call, the default slippage is 75% of the bid ask width; for a 2 leg trade like a put spread vertical the slippage would be 66% of the total bid-ask spreads; for a 3 leg trade like a butterfly, slippage would be56% of the bid-ask width for all legs; and finally a 4 leg iron condor would have a slippage of 53%.