Help me understand Forex in Interactive Brokers

External question — Personal Finance Stack Exchange Author: ggambetta Original post: https://money.stackexchange.com/questions/24640 License: CC BY-SA 3.0 — https://creativecommons.org/licenses/by-sa/3.0/ Adaptation: HTML converted to plain text; contact email addresses removed. I have a CHF-based account in Interactive Brokers. I wanted to buy VEUR in LSE, which trades in GBP. I entered an order, I was told I didn't have enough GBP. Fair enough. I asked the live chat how to do this, and I was told to do a Forex trade. So I bought some GBP with the CHF (let's say 1000 GBP), bought VEUR in GBP, and so I was left with some GBP in the account (let's say 10 GBP). In the Home/Positions tab I can see the VEUR, the CHF, and the leftover 10 GBP. So far so good. What I don't understand is when I go to Trade/Quicktrade, the Positions section shows an open position for the GBP ( GBP, Cash, IDEALPRO, CHF ) but for the original amount of 1000 GBP, not for the leftover 10. If I click the Close button, it creates an order to sell 1000 GBP, which I don't have! What's going on? I thought I was selling CHF, buying GBP, and then buying stock, as if I went to a (physical) exchange and bought some currency. This open position makes me thing something else may be going on (am I somehow borrowing currency from IB?). I'm really afraid of doing this wrong and ending up losing a lot of money or paying interest or whatever.