I opened a large position of a calendar call spread that was fairly DITM for BYND. The position was opened on July 30. I was concerned that I would be assigned on the short call for the calendar. I called IB several times after market was closed to see if I was assigned. The representative told me that there were no shares to borrow and if the short calls where assigned, IB would buy it in the open market to cover. It didn't sound so bad to me as I was more concerned with the hard to borrow fee. I was frequently checking my IBKR mobile just in case to see if the options got assigned which would afford me the ability to buy back the shares in after market which is the same day to avoid the borrowing fee. On July 30, the borrowing fee for BYND was about 190%. On July 31st at approx 2am, I see that the short call option was assigned and I was short a substantial amount of BYND. Of course, when the market opened, IB quickly auto liquidated to buy back the short position of BYND. I was thinking that since IB auto liquidated the same day, there would be no borrow fee. Later in the day, I recieved a notification that the short call option was exercised on July 30 with that trade date. Worst is that the borrow fee was based on the settlement date of Aug 1 which turns out to be 386%. The borrowed fee for 1 day was 15k which was absurd. Im hoping someone can point me in the right direction or provide me with advice as I am in Canada and not familiar with the regulation in US. Basically, when options are assigned, you have no way knowing or provided the ability to cover until next day which means the borrowing fee is applied. How can IB show the option assignment on my trade log and portfolio as July 31 at 2am yet value the trade date as on July 30? I understood the risk of being assigned before expiration with the intention of buying back the shares to convert immediately. What bothers me is the fact that I had no opportunity to be notified on the same day. I had thought that option assignment after market closed which would be the next business day. Any help would greatly be appreciated. Thank you.