To begin, I don't want to sound like I'm bashing IB. I've been a customer of theirs for 3 years and have been happy in the past. This is the first major problem I've had with them. I just felt it would be a good idea to put it out in the public. This way it gives IB the opportunity to shine and do the right thing. The alternative is that I get screwed Here's the situation. Last Friday, July 21st, I was long 20 JUL ES 1250 Puts and short 20 JUL ES 1245 Puts. The closing price for the SEP ES was below 1245 (1244.50 I think). So, obviously my 1245 strike is very close so I have some pin risk. I'm concerned about assignment because I don't want to wake up and be short 20 ES contracts. So as soon as Globex opens on Sunday night I check my account and it is flat with the expected profit from the debit spread showing as cash in my account. I then checked the official IB statement through my Account Management which shows that all 20 ES 1245 Puts were assigned and that I am indeed flat. Now the plot thickens. I wake up Monday morning and I find to my surprise that I am short 10 ES contracts and the ES has now moved 12.5 points away from the 1245 strike I was supposed to be assigned at. After speaking with a gentleman from customer service he informs me that they made a mistake and I was only assigned on 10 of the 20 short 1245 Puts. He then recommended that I liquidate my unexpected position (which has now lost me over 6K) and open a ticket with them through their website. He said that after reviewing it (7-10 days) they should reimburse me. Like I said, I'm not bashing IB. I understand mistakes will be made. I'm hoping IB will do the right thing in my mind and reimburse me for my loss. I feel this way not because I wasn't assigned on the 1245 Puts but because I was informed through my account and through my statement that I was indeed assigned and flat. I'm sure there will be diehard IB fans out there that will tell me that just because my account and my statement show that I'm flat, it doesn't mean that I am. I won't have any argument for this because I don't see the logic in it. All I know is that my statement said I was flat as did my account. On Monday morning IB customer service tells me that "they" made an error and that I was only assigned on half my outstanding short 1245 Puts. The key point here is that they made the error and therefore they should be liable for my loss in this situation. I do hope IB does the right thing because I would like to continue being a satisfied customer of theirs.