Quote from JackR:
As I understand the IB forex system, IB has a small standalone network set up on which some banks and all customers may enter offers to buy and sell. It is not, to the best of my knowledge, tied to the interbank forex system, but is tied to some banks that deal in the inter-bank forex market. So I doubt that your the trade would appear on Bloomberg or Reuters.
IB states that they are the counter-party to their customers' forex trades:
The off-exchange foreign currency trading you are entering into is not conducted on an interbank market, nor is it conducted on a futures exchange subject to regulation as a designated contract market by the Commodity Futures Trading Commission ("CFTC"). The foreign currency trades you transact are trades with the futures commission merchant or retail foreign exchange dealer as your counterparty. WHEN YOU SELL, THE DEALER IS THE BUYER. WHEN YOU BUY, THE DEALER IS THE SELLER. As a result, when you lose money trading, your dealer is making money on such trades, in addition to any fees, commissions, or spreads the dealer may charge.
https://www.interactivebrokers.com/...tration_1/forex_mult_curr_risk_disclosure.jsp