All of a sudden I discovered this beautiful feature: accrued interest. Whenever I looked at my monthly IB statements I always saw "accrued interest = -5" or "accrued interest = -10" dollars, but I thought it was just some detail I would never understand... and that there was no way that IB would charge me for anything other than the data fees. Well, I was wrong. I had a positive USD balance, and they didn't charge me accrued interest for that of course, but I also had a (smaller) negative EUR balance, I don't know for what reason, since I never traded anything in euros. That cost me about 7 dollars a month for years, for a total of hundreds of dollars. I called customer service at IB and they told me ... I don't remember if it was to buy or to sell euros, but it is now fixed because it says "EUR 0", while for years it said EUR -1100. Still, now in TWS it says I have an open FOREX trade, and puzzles me. Can anyone please explain to me the following: 1) why did I get a negative euro balance when I didn't even trade anything that EUR as a currency and my base currency is USD. 2) why didn't IB warn me that I was getting charged about one hundred dollars a year in accrued interest. 3) how can it even happen that you have an overall positive balance and get charged accrued interest. 4) how come I have an open FOREX trade now that I closed the negative EUR balance (in a sense it looks as though my account was normal with a negative euro balance, because at least I didn't have any open trades).