So to be clear, IB doesn't charge you to hold Euros or CHF, right? If you opened a Euro or CHF denominated account and parked your Euro's or CHF in that account you wouldn't be charge any more than the regular account fees. If you want to hold a long Euro or CHF and short dollar position they charge, but that's simply a factor of the differential interest rate and would happen even if interest rates were 20% on one and 18% on the other. In fact because IB kills you on the buy/sell interest rate they'd charge you if it was 20% on both.
Nope, IB does charge you on idle EUR and CHF cash balance above 100k, it has been going on for a while. I had quite a bit of EUR cash sitting in an IB account when that started, and decided to invest and exchange the euros to avoid the charge, and from memory in 2017 it wasn't a great idea. Still get charged once in a while when I keep the balance over 100k, moving back to Europe soon, might keep some euros cash in the new bank there. https://www.interactivebrokers.com.hk/en/index.php?f=1595 check " Interest Paid on Idle Cash Balances " in the link above.
EUR 0 - 100,000 0% 100,000.01 + -0.883% (BM - 0.25%) CHF 0 - 100,000 0% 100,000.01 + -1.236% (BM - 0.25%)
You're welcome, besides you are right the way IB calculates interests/swap on forex trades is very painful to its customers - at least those who hold the positions overnight.
%% I didnt realize they favored USD so much; as far as paying interest/$/ paid daily ,that link notes.