I have had several shorts bought in on me, including three with no prior notice of any type until they showed up on my nightly trade confirmations. Sometimes an email and a TWS message are sent on shorts that might be bought in. Sometimes the nightly confirmation is a posting for a future trade that will occur after market open the next day. In that case the price will be adjusted the next day. I have had positions bought in the morning with no notice until that night. Buy-ins can happen at anytime and are done at market. On SYUT, a thin stock trading around $20-22, covering 287 shares cost $1 more than I could have done myself with limits and a little patience. Buying at market can be very bad for a position of size, especially in a thinly quoted stock, especially on ARCA. I understand this is what IB feels it has to do to meet legal requirements, but it seriously compromises my ability to manage short positions. It is now quite possible to cover the same position twice resulting in a net long. My response has been to get smaller. At a minimum IB needs to provide real-time notice of buy-ins.